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Are blood flow and lipolysis in subcutaneous adipose tissue influenced by contractions in adjacent muscles in humans?
Abstract
Aerobic exercise increases whole body adipose tissue lipolysis, but is lipolysis higher in subcutaneous adipose tissue (SCAT) adjacent to contracting muscles than in SCAT adjacent to resting muscles? Ten healthy, overnight-fasted males performed one-legged knee extension exercise at 25% of maximal workload (W(max)) for 30 min followed by exercise at 55% W(max) for 120 min with the other leg and finally exercised at 85% W(max) for 30 min with the first leg. Subjects rested for 30 min between exercise periods. Femoral SCAT blood flow was estimated from washout of (133)Xe, and lipolysis was calculated from femoral SCAT interstitial and arterial glycerol concentrations and blood flow. In general, blood flow and lipolysis were higher in femoral SCAT adjacent to contracting than adjacent to resting muscle (time 15-30 min; blood flow: 25% W(max) 6.6 +/- 1.0 vs. 3.9 +/- 0.8 ml x 100 g(-1) x min(-1), P < 0.05; 55% W(max) 7.3 +/- 0.6 vs. 5.0 +/- 0.6 ml x 100 g(-1) x min(-1), P < 0.05; 85% W(max) 6.6 +/- 1.3 vs. 5.9 +/- 0.7 ml x 100 g(-1) x min(-1), P > 0.05; lipolysis: 25% W(max) 102 +/- 19 vs. 55 +/- 14 nmol x 100 g(-1) x min(-1), P = 0.06; 55% W(max) 86 +/- 11 vs. 50 +/- 20 nmol x 100 g(-1) x min(-1), P > 0.05; 85% W(max) 88 +/- 31 vs. -9 +/- 25 nmol x 100 g(-1) x min(-1), P < 0.05). In conclusion, blood flow and lipolysis are generally higher in SCAT adjacent to contracting than adjacent to resting muscle irrespective of exercise intensity. Thus specific exercises can induce "spot lipolysis" in adipose tissue.
... 17 The mechanism for electromagnetically induced fat reduction is speculative and extrapolated from a 2007 Danish exercise physiology study. 32 The theory is that vigorous muscle contractions lead to hypertrophy, plus a reduction of local fat by increased metabolism. 18 These Danish subjects were not treated with an energy-based device. ...
... Not surprisingly, volunteer men exercising their lower extremities experienced increased blood flow and a 1°C temperature increase in the exercising thigh muscles. 32 This increased blood flow is believed to overlap to the adjacent adipose tissue, exposing this fatty tissue to higher levels of circulating epinephrine. 32 Stallknecht et al 32 speculate that paracrine factors, such as interleukin 6, may be released from the contracting muscles, diffuse into local tissues, and produce "spot lipolysis." ...
... 32 This increased blood flow is believed to overlap to the adjacent adipose tissue, exposing this fatty tissue to higher levels of circulating epinephrine. 32 Stallknecht et al 32 speculate that paracrine factors, such as interleukin 6, may be released from the contracting muscles, diffuse into local tissues, and produce "spot lipolysis." A problem with this theory is that circulating catecholamines influence all adipose tissue deposits in the body, not just adipose tissue adjacent to contracting muscles. ...
Background:
Energy-based treatments include ultrasound, lasers, cryolipolysis, and radiofrequency. The most recent energy treatment for noninvasive body contouring is electromagnetic treatments-a hot topic in plastic surgery today. A systematic review to assess efficacy and safety has not been published.
Methods:
An electronic search was performed using PubMed to identify the literature describing electromagnetic treatments. Measurements from imaging studies were tabulated and compared.
Results:
Fourteen clinical studies were evaluated. Two studies included simultaneous radiofrequency treatments. In 11 studies, the Emsculpt device was used; in 2 studies, the Emsculpt-Neo device was used. One study included a sham group of patients. The usual protocol was 4 treatments given over a 2-week period. No complications were reported. Eight studies included abdominal measurement data obtained using magnetic resonance imaging, computed tomography, or ultrasound. Photographic results were typically modest. Photographs showing more dramatic results also showed unexplained reductions in untreated areas.Measurement variances were high. The mean reduction in fat thickness was 5.5 mm. The mean increment in muscle thickness was 2.2 mm. The mean decrease in muscle separation was 2.9 mm (P = 0.19). Early posttreatment ultrasound images in 1 study showed an echolucent muscle layer, compared with a more echodense layer at the baseline, consistent with tissue swelling after exercise. Almost all studies were authored by medical advisors for the device manufacturer.
Discussion:
Measurement data show small reductions in fat thickness, occurring almost immediately after the treatments. Adipocyte removal without tissue swelling would be unique among energy-based treatments. Similarly, muscle hypertrophy is not known to occur acutely after exercise; muscle swelling likely accounts for an early increment in muscle thickness. Any improvement in the diastasis recti is likely fictitious.
Conclusions:
Electromagnetic treatments, either administered alone or in combination with radiofrequency, are safe. However, the evidence for efficacy is tenuous. Measured treatment effects are very small (<5 mm). Conflict of interest and publication bias are major factors in studies evaluating energy-based alternatives. The evidence-based physician may not be satisfied that an equivocal treatment benefit justifies the time and expense for patients.
... comparing arms and legs); ii) for the same body fat depot, significant inter-individual differences might occur. For example, abdominal fat may respond differently to exercise in male compared to female [28, 75,76]; iii) contrary to neuromuscular-related outcomes, there is no evidence for a cross-education between subcutaneous fat depots through exercise; iv) the effects of exercise training on one limb compared to the contralateral non-exercised limb allow a tight control for dietary (even if this is not manipulated) and other possible intervening factors (e.g., methodology; seasonal variation; genetic; biology; variations in attention and motivation between experimental and control groups) [46,69]; v) studies seeking to validly test the hypothesis of spot reduction should consider the size of the adipose tissue depots adjacent to the trained and respective non-trained muscles before and after an intervention period (with a relatively high volume of work to impact fat tissue) not just after an acute exercise bout [14]; vi) valid studies should use valid measurement techniques, avoiding techniques that may provide biased results due to changes in muscle mass [18] or other factors not related to biological changes in fat content [77]. For example, reductions between 3-14% (mean 7.5%) were noted in the trained arm compared to the non-trained arm when subcutaneous fat was measured in the biceps using a skinfold calliper [18]. ...
... In contrast to our proposed definition and model to test the hypothesis of exercise-induced localized fat reduction, two cross-sectional studies [14,17] found acute localized lipolysis. However, the studies did not demonstrate spot reduction (i.e., localized reduction of adipose tissue). ...
... However, the studies did not demonstrate spot reduction (i.e., localized reduction of adipose tissue). Moreover, the two aforementioned cross-sectional studies [14,17], although found that exercising one leg promoted an increase in lipolysis in the subcutaneous fat adjacent the muscles being exercised (e.g., anterior thigh), the effect was highly local, meaning that any significant long-term effect (i.e., fat reduction) would be unlikely. Further, compared to the aforementioned cross-sectional studies [14,17], some authors have found contradicting findings, with intense exercise (e.g., resistance training) reducing subcutaneous adipose tissue blow flood and lipolysis [31]. ...
Purpose
The process in which specific exercises reduce localized adipose tissue depots (targeted fat loss) and modify fat distribution is commonly termed spot reduction. According to this long-held popular belief, exercising a limb would lead to greater reduction in the adjacent adipose tissue in comparison with the contralateral limb. Aside from popular wisdom, scientific evidence from the 20th and 21st century seems to offer inconclusive results. The study aim was to summarize peer-reviewed literature assessing the effects of unilateral limb training, compared with the contralateral limb, on the localized adipose tissue depots in healthy participants, and to meta-analyse its results.
Methods
We followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. We searched PubMed, Web of Science, and Scopus electronic databases using several relevant keyword combinations. Independent experts were contacted to help identify additional relevant articles. Following the PICOS approach, we included controlled studies that incorporated a localized exercise intervention (i.e., single-leg training) to cohorts of healthy participants (i.e., no restriction for fitness, age, or sex) compared with a control condition (i.e., contralateral limb), where the main outcome was the pre-to-post-intervention change of localized fat. The methodological quality of the studies was assessed with the Physiotherapy Evidence Database scale. Pre- and post-intervention means ± standard deviations of the fat-related outcome in the trained and control groups (limbs) were converted to Hedges’ g effect size (ES; with 95% confidence intervals [CI]) by using a random-effects model. The impact of heterogeneity was assessed with the I<SUP>2</SUP> statistic. Extended Egger’s test served to explore the risk of reporting bias. The statistical significance threshold was set at p < 0.05.
Results
From 1833 search records initially identified, 13 were included in the meta-analysis, involving 1158 male and female participants (age, 14–71 years). The 13 studies achieved a high methodological quality, and presented results with low heterogeneity (I<SUP>2</SUP> = 24.3%) and no bias (Egger’s test p = 0.133). The meta-analysis involved 37 comparisons, with 17 of these favouring (i.e., greater reduction of localized fat) the trained limb, and 20 favouring the untrained limb, but the ES ranged between –1.21 and 1.07. The effects were consistent, with a pooled ES = –0.03, 95% CI: –0.10 to 0.05, p = 0.508, meaning that spot reduction was not observed.
Conclusions
Localized muscle training had no effect on localized adipose tissue depots, i.e., there was no spot reduction, regardless of the characteristics of the population and of the exercise program. The popular belief concerning spot reduction is probably derived from wishful thinking and convenient marketing strategies, such as influencers seeking increased popularity and procedure sellers interested in increasing advertising.
... It has particular significance for exercise performance, because it directly influences both the supply of working muscles with energy substrates and the clearance of metabolites such as lactate (74). In addition, there is also a dependency of certain types of metabolism on Q (56,66,88,91), which are discussed below. ...
... Capillary perfusion has been outlined as a determinant for fatty acid metabolism (66,91). Because fatty acid oxidation is restricted during exercise at high intensities (88), it is likely that mechanisms causing oxidative adaptations in terms of fatty acid oxidation take effect in the resting interval of an interval training session and profit from the elevated microvascular perfusion. ...
... This increases the capillary surface area (85), which facilitates local gas exchange. Further, recent studies reported that a higher local muscle perfusion is associated with an enhanced oxidative metabolism like fatty acid oxidation (56,66,88,91). Consequently, especially fatty acid oxidation could be enhanced by improved post-exercise O 2 availability during the early recovery phase or, with regard to interval training, during the low interval. ...
Interval training evidentially triggers aerobic adaptions like improved fatty acid and
carbohydrate oxidation rates. Increased local blood supply is supposed to be one
important mechanism that underlies these effects. Two important determinants of
interval training are intensity and duration of work intervals. However, knowledge is
scarce on the detailed effect of exercise intensity (Study 1) and exercise duration
(Study 2) on the other hand on post-exercise blood supply and oxygen availability. In
order to study those issues, the effects of six different, interval training associated
exercise intensities and durations on post-exercise musclular oxygen availability and
relative changes in hemoglobin concentration have been examined.
For both (1) and (2), relative changes in oxygenated and deoxygenated hemoglobin
and total hemoglobin (ΔO2Hb, ΔHHb, ΔTHb) were monitored with near-infrared
spectroscopy of the vastus lateralis muscle and pulmonary oxygen uptake (VO2) was
assessed. In Study 1, 17 male subjects performed an experimental protocol
consisting of 180 s cycling bouts at six exercise intensities (40–90% peak oxygen
uptake, VO2peak) in randomized order, separated by 5 min rests. In order to estimate
local muscle blood supply and oxygen provision, ΔHHb/ΔVO2 ratio and estimated
capillary blood flow (Qcap) were calculated during recovery using a bi-exponential
model. In Study 2, 18 healthy male subjects performed an experimental protocol of
five exercise bouts (30 s, 60 s, 90 s, 120 s and 240 s) at 80% VO2peak in randomized
order, separated by 5 min rests. To examine the influence of submaximal aerobic
performance, subjects with gas exchange thresholds (GET) above 60% VO2peak
(GET60+) were compared with subjects reaching GET below 60% VO2peak (GET60-).
The results of Study 1 revealed a progressively increased ΔHHb/ΔVO2 ratio from
40% to 60% VO2peak. Above 60% VO2peak, it decreased progressively. Post-exercise
ΔTHb and ΔO2Hb showed an overshoot in relation to pre-exercise values, which was
equal following exercise at 40–60% VO2peak and rose significantly following higher
exercise intensities. A plateau was reached following exercise at ≥80% VO2peak.
Mean response time (MRT) of Qcap recovery increased significantly with increasing
exercise intensity. Study 2 showed significantly increased post-exercise oxygen
2
availability and local blood supply following 90 s exercise duration without a further
increase following longer exercise bouts. Considering submaximal aerobic
performance, the GET60+ group reached maximum post-exercise oxygen availability
also with shorter exercise (60 s) than the GET60- group (90 s).
Based on the results, Study 1 shows a progressively increasing mismatch of local O2
delivery and utilization with increasing exercise intensity up to 60% VO2peak after 3
min exercise bouts as suggested by increasing end-exercise ΔHHb/ΔVO2 ratio. This
suggests that microvascular perfusion does not adequately meet the increased
metabolic demand up to this point. Interestingly, ΔHHb/ΔVO2 decreased above 60%
VO2peak. Consequently, the matching of HHb and VO2 gets progressively impaired
from 40% VO2peak to 60% VO2peak but is progressively improved at exercise intensities
above 60% VO2peak up to 90% VO2peak. Postexercise oxygen availability also was
improved above above 60% VO2peak, which was according to the transition from
moderate to heavy intensity exercise (gas exchange threshold 59 ± 13% VO2peak).
Consequently, beginning acidosis could have promoted local vasodilation. Study 2
results give evidence for a slower adjustment of local vasodilation in subjects with
GET60- than GET60+. The key mechanism behind those effects presumably is an
enhanced endothelium and flow-mediated vasodilation superimposing sympathetic
vasoconstriction.
These results suggest that cycling exercise is most efficient for enhancing local
postexercise oxygen availability and blood supply when it is conducted (A) at least at
80% VO2peak and (B) with a minimum duration of 90 s for subjects wit GET60- while
such with GET60+ have same effects following 60 s of exercise. Hence, interval
training should be prescribed accordingly in order to promote aerobic effects.
... of exercise as compared to gluteal 3 and clavicular ScaT, even when aerobic exercise was conducted with the upper limb. 4 Mechanisms underpinning such regional differences have been identified in a site-specific sensitivity to exercise-induced catecholamine stimulation, which suggests an independent regulation of regional adipose tissue depots. 5 hence, owing the consequent metabolic implications of fat distribution modifications, along with the attraction of aesthetic body sculpting the hypothesis of localised fat mass loss by targeted exercise (also known as "spot slimming") has gained interest overtime. ...
... Kostek et al. 10 for instance, failed to detect any significant regional ScaT reduction, as assessed by magnetic resonance imaging, after 12 weeks of resistance training of the non-dominant arm, in spite of a significant skinfold reduction. in contrast, data supporting the possibility of regional lipolysis were reported by Stallknecht et al.,4 who found that during one-leg endurance exercise, adipose tissue blood flow and interstitial glycerol concentration were greater in the aT adjacent to the contracting muscles, compared to the aT in the resting muscles. ...
... 6 The Journal of SporTS Medicine and phySical fiTneSS 799 nevertheless, it is noteworthy that the exercise protocol adopted in the present investigation was different from those used in the aforementioned studies, which may relate to the discrepancies observed. indeed, the specificity of the exercise response was highlighted in an elegant study by Stallknecht et al.,4 comparing one-leg knee extension exercise at different exercise intensities using the microdialysis and 133 Xe washout technique, in which they showed that lipolysis in ScaT adjacent to contracting muscle was acutely stimulated by exercise and associated with an increased adipose tissue blood flow. Notably, leg SCAT lipolysis was higher at the highest exercise intensity (85% W max ), along with an increased arterial epinephrine concentration. in this vein, Trapp et al. 20 compared the effect of steady state cycling exercise training at 60% Vo 2max with a high intensity intermittent cycling exercise on adipose tissue and its distribution in young women. ...
Background:
The present study tested the possibility of a localized fat mass (FM) reduction by means of training programmes focusing on specific bodily regions.
Methods:
Sixteen physically inactive women (age: 31±4; BMI: 27.5±2.1), randomly allocated to two groups, completed an 8 week training programme. In one group (UpBdResist) training sessions consisted of upper body resistance exercises followed by 30-minute cycling at 50%VO2max, while the other group (LwBdResist) performed lower body resistance exercises followed by 30 minutes on an arm-ergometer. Regional body composition was assessed by DEXA and skin fold measures.
Results:
Regardless of a similar reduction in both groups, UpBdResist training elicited a greater reduction of the upper limbs (UL) FM as compared to the lower limbs (LL) (Δ% UL vs. LL: -12.1±3.4 vs. -4.0±4.7; P=0.02). Conversely, in the LwBdResist group, FM loss was more pronounced in the LL as compared to the UL (Δ% UL vs. LL: -2.3±7.0 vs. -11.5±8.2, P=0.02). Likewise, LwBdResist elicited a larger effect on lean mass (LM) of the LL as compared to UL (Δ% LL vs. UL: +8.4±5.8 vs. -2.7±5.0, P<0.01), yet no differences between upper and lower limb LM changes were detected in UpBdResist group.
Conclusions:
The present data suggest that a training programme entailing localized explosive resistance exercise, prior to an endurance exercise bout, may target specific adipose tissue sites eliciting localised fat mass loss in the upper and lower limbs.
... Local power exercises can hardly be used for spot reduction of fat reserves above trained muscle [11]. Bente Stallknecht et al. [20] notes possibility of speculations with conclusions and statistic error in processing of biopsy data. Besides, we can not understand reasons of insignificant increase of fat cells' mass with unchanged thickness of SF in not trained leg. ...
... In all cases blood circulation and lipolysis were higher in SF adhering working muscle. Thus, specific exercises can cause spot lipolysis in fat tissue [20]. ...
... Actually only main metabolism can be supplied by fat oxidation [12]. 2. Lipolysis increase [20] is only initial link of fat utilization as source of energy. More durable and energetically effective fat oxidation in Krebs's cycle has not been researched. ...
Purpose: to work out recommendations on choosing of exercises for power conditional trainees, considering decrease of fat mass percentage as the purpose. Methods: analysis of changes of body composition of trainees, practicing different kinds of conditional power training. Results: the data about influence of different physical loads on thickness of subcutaneous fat in different parts of body have been generalized. Recommendations on choosing of exercises for power conditional trainees for body composition improving have been presented. It was found that fat loss occurs quicker in upper part of body (subcutaneous and visceral). This is observed with increasing of motor functioning and reducing calories of eating. When training any separate muscular group changes of subcutaneous fat take place not compulsory in body parts, in which the trained group is located. Conclusions: it is purposeful to mainly use basic (multi-joint) exercises in power conditional training.
... Several studies have evaluated the effects of specific localized exercise on whole-body and regional tissue composition, with contradicting results. Some studies have reported that after exercise intervention, localized mobilization of subcutaneous fat may be observed (15,18,19,21), whereas others have not found these changes (6,9,10,12,17,23). The conflicting results may be accounted for by the methodology used in the studies cited. ...
... A valid study design to test the hypothesis of spot reduction would be one in which the muscles in one part of the body are trained, whereas the muscles in the contralateral side are not. In addition, the size of the adipose tissue depots adjacent to the trained and respective sedentary muscles should be carefully monitored before and after the intervention period (21) using valid measurement techniques, such as fat biopsy, dual-emission x-ray absorptiometry (DXA), or magnetic resonance image techniques (10). Some of the previous studies cited met these criteria (10,12); nevertheless, because of the training protocol used (i.e., low training volume), localized blood flow and lipolysis possibly remained limited in the adipose tissue depot adjacent to the trained muscle group (21). ...
... In addition, the size of the adipose tissue depots adjacent to the trained and respective sedentary muscles should be carefully monitored before and after the intervention period (21) using valid measurement techniques, such as fat biopsy, dual-emission x-ray absorptiometry (DXA), or magnetic resonance image techniques (10). Some of the previous studies cited met these criteria (10,12); nevertheless, because of the training protocol used (i.e., low training volume), localized blood flow and lipolysis possibly remained limited in the adipose tissue depot adjacent to the trained muscle group (21). Thus, it remains to be determined whether spot reduction is possible through localized exercise sessions with a sufficient training volume component after a longitudinal exercise intervention. ...
The purpose of this study was to examine the effects of a localized muscle endurance resistance training program on total body and regional tissue composition. Seven men and four women (23±1 years of age) trained with their non-dominant leg during 12 weeks, three sessions per week. Each session consisted of 1 set of 960-1,200 rep (leg press exercise), at 10-30% 1RM. Before and after training, body mass, bone mass, bone mineral density, lean mass, fat mass and fat percentage were determined by dual-emission X-ray absorptiometry. Energy intakes were registered, by using a food recall questionnaire. At the whole body level, body mass, bone mass, bone mineral density, lean mass or body fat percentage were not significantly changed. However, body fat mass significantly decreased by 5.1% (pre 13.5±6.3 kg, post 12.8±5.4 kg; P<0.05). No significant changes in bone mass, lean mass, fat mass or fat percentage were observed in both the control and trained leg. A significant (P<0.05) decrease in fat mass was observed in the upper extremities and trunk (10.2 and 6.9%, respectively, P<0.05). The reduction of fat mass in the upper extremities and trunk was significantly greater (P<0.05) than the fat mass change observed in the trained leg, but not vs. the control leg. No significant changes were observed in energy intake pre and post exercise intervention (2,646±444 kcal•day and 2,677±617 kcal•day, respectively). In conclusion, the training program was effective in reducing fat mass, but this reduction was not achieved in the trained body segment. The present results expand the limited knowledge available about the plastic heterogeneity of regional body tissues when a localized resistance training program is applied.
... The release of fatty acids from adipose tissue during exercise is potentially influenced by adipose tissue lipolysis, the rate of fatty acid reesterification, and adipose tissue blood flow (ATBF). Measurements in vivo in a range of different subjects and exercise protocols using microdialysis (8,176,178,242) and arteriovenous (a-v) difference (5,100,237,240) provide direct evidence that fatty acids are mobilized from SCAT during exercise. At least part of the increase during exercise appears to be due to decreased rates of fatty acid reesterification (100,206). ...
... As the duration of fixed-intensity exercise increases, there is an increase in both whole body lipolytic rate (for a review, see Ref. 104) and also directly determined regional adipose tissue lipolysis (237,240,242). This may be the product of slow-acting hormones such as growth hormone and cortisol (56,87,90). ...
... There is some evidence that this effect of exercise may be region-specific, with an increase in subcutaneous abdominal ATBF in response to cycling exercise but no change in femoral ATBF (106). However, other studies have shown that femoral ATBF does respond to a leg extension exercise model (237). Interestingly, one investigation showed that pathway. ...
Physical activity and exercise are key components of energy expenditure and therefore of energy balance. Changes in energy balance alter fat mass. It is therefore reasonable to ask: What are the links between physical activity and adipose tissue function? There are many complexities. Physical activity is a multifaceted behavior of which exercise is just one component. Physical activity influences adipose tissue both acutely and in the longer term. A single bout of exercise stimulates adipose tissue blood flow and fat mobilization, resulting in delivery of fatty acids to skeletal muscles at a rate well-matched to metabolic requirements, except perhaps in vigorous intensity exercise. The stimuli include adrenergic and other circulating factors. There is a period following an exercise bout when fatty acids are directed away from adipose tissue to other tissues such as skeletal muscle, reducing dietary fat storage in adipose. With chronic exercise (training), there are changes in adipose tissue physiology, particularly an enhanced fat mobilization during acute exercise. It is difficult, however, to distinguish chronic "structural" changes from those associated with the last exercise bout. In addition, it is difficult to distinguish between the effects of training per se and negative energy balance. Epidemiological observations support the idea that physically active people have relatively low fat mass, and intervention studies tend to show that exercise training reduces fat mass. A much-discussed effect of exercise versus calorie restriction in preferentially reducing visceral fat is not borne out by meta-analyses. We conclude that, in addition to the regulation of fat mass, physical activity may contribute to metabolic health through beneficial dynamic changes within adipose tissue in response to each activity bout.
... Evidence pointing to local regulation of ATBF comes from a recent study showing that ATBF increases only in a close proximity of the contracting quadriceps muscle and not in the contralateral resting leg (17). The authors speculated that this increase in blood flow was attributable to elevated muscle temperature only in adipose regions adjacent to working muscle. ...
... Stallknecht et al. (17) recently reported that blood flow increases only in subcutaneous adipose tissue close to working skeletal muscle from rest to exercise irrespective of exercise intensity, but not in the adipose tissue of contralateral resting leg. Our findings in the present study fit well with these previous results and further extend the findings on two important points. ...
... functions ultimately to supply the adjacent muscle with energy substrates or that the increases in blood flow in both tissues are coincident responses to muscle contraction. In addition to this, however, it is likely that if exercise workloads had been increased beyond 150 N, which was the highest exercise intensity in the present study, increase in adipose blood flow would have been leveled off (17), whereas muscle blood flow is well known to increase with increasing exercise intensity up to maximal intensities. Thus exactly similar metabolic regulatory mechanisms that are thought to work in muscle may not directly apply to adipose tissue. ...
Regulation of subcutaneous adipose tissue blood flow (ATBF) remains poorly elucidated in humans, especially during exercise. In the present study we tested the role of adenosine in the regulation of ATBF adjacent to active and inactive thigh muscles during intermittent isometric knee-extension exercise (1 s contraction followed by 2 s rest with workloads of 50, 100, and 150 N) in six healthy young women. ATBF was measured using positron emission tomography (PET) without and with unspecific adenosine receptor inhibitor theophylline infused intravenously. Adipose regions were localized from fused PET and magnetic resonance images. Blood flow in subcutaneous adipose tissue adjacent to active muscle increased from rest (1.0 ± 0.3 ml·100 g(-1)·min(-1)) to exercise (P < 0.001) and along with increasing exercise intensity (50 N = 4.1 ± 1.4, 100 N = 5.4 ± 1.8, and 150 N = 6.9 ± 3.0 ml·100 g(-1)·min(-1), P = 0.03 for the increase). In contrast, ATBF adjacent to inactive muscle remained at resting levels with all intensities (∼1.0 ± 0.5 ml·100 g(-1)·min(-1)). During exercise theophylline prevented the increase in ATBF adjacent to active muscle especially during the highest exercise intensity (50 N = 4.3 ± 1.8 ml·100 g(-1)·min(-1), 100 N = 4.0 ± 1.5 ml·100 g(-1)·min(-1), and 150 N = 4.9 ± 1.8 ml·100 g(-1)·min(-1), P = 0.06 for an overall effect) but had no effect on blood flow adjacent to inactive muscle or adipose blood flow in resting contralateral leg. In conclusion, we report in the present study that 1) blood flow in subcutaneous adipose tissue of the leg is increased from rest to exercise in an exercise intensity-dependent manner, but only in the vicinity of working muscle, and 2) adenosine receptor antagonism attenuates this blood flow enhancement at the highest exercise intensities.
... The term "spot reduction" describes the targeted local reduction of subcutaneous fat tissue as a result of speciWc exercises in that area of the body. The results of these studies are not clear (Kostek et al. 2007;Walts et al. 2008;Stallknecht et al. 2007). Stallknecht et al. (2007) addressed the question of whether blood Xow and lipolysis of the subcutaneous fat tissue were aVected by the activity of adjacent muscles. ...
... The results of these studies are not clear (Kostek et al. 2007;Walts et al. 2008;Stallknecht et al. 2007). Stallknecht et al. (2007) addressed the question of whether blood Xow and lipolysis of the subcutaneous fat tissue were aVected by the activity of adjacent muscles. The local perfusion of the subcutaneous fat tissue was determined by the 133Xe washout technique. ...
... The increased lipolysis and blood Xow in the femoral adipose tissue could be due to an increase in local temperature (Felländer et al. 1996;Astrup et al. 1980). Another possible explanation for increased lipolysis could be that norepinephrine levels increase locally with increased blood Xow (Stallknecht et al. 2007). ...
The purpose of this study was to determine whether physical activity, with and without lower body pressure, leads to increased regional fat loss in the lower extremities of overweight females. Eighty-six obese women with a female phenotype were randomly assigned into four groups: control group (C), diet only (D), diet plus exercise (DE) or diet, exercise and lower body pressure intervention (DEP). The three treatment groups followed the same diet, the two exercise groups (DE and DEP) additionally followed an endurance training program of 30 min of cycling at 50%VO(2)max three times per week with or without lower body pressure. Body composition and fat distribution were assessed by DXA. Body size circumference measurements were recorded as well as subjective ratings of cellulite and skin appearance. As expected, all test groups (D, DE, DEP) showed a significant decrease (p < 0.05) in total body mass and fat mass. DXA revealed significant differences between the experimental groups and C. The DEP group also lost significantly more body mass and fat mass when compared with D, while no significant difference was observed between the other groups. A similar pattern was seen for circumference measurement data. A significant perceived improvement was made by the DEP group when compared with C, D and DE groups for skin condition and also between the DEP versus C and D groups for cellulite. The combination of diet and exercise is successful for weight reduction. The additional application of lower body pressure especially affects skin appearance.
... More recently, Stallknecht and coll. [19], hypothesized that exercise on specific muscles may induce "spot lipolysis" via an increased blood flow and release of fatty acids in the SAT nearby the contracting muscle regardless of exercise intensity. However, most of the studies found conflicting conclusions: some authors found a positive effect of spot reduction on localized lipolysis [20][21][22], while others were inconclusive [23][24][25][26]. ...
... However, it was recently observed that lipolytic activity is associated with an increase of blood flow in the adipose tissue and, thus, to the oxygenation of the adipocyte, suggesting that "blood flow and lipolysis are generally higher in subcutaneous adipose tissue adjacent to contracting than adjacent to resting muscle irrespective of exercise intensity. Thus, specific exercises can induce "spot lipolysis" in adipose tissue" [19]. Based on these premises, the goal of spot reduction training should be to increase blood perfusion in the areas where it is most needed, which are where the adipose tissue is located; and sequentially promote fat oxidation. ...
Accumulation of adipose tissue in specific body areas is related to many physiological and hormonal variables. Spot reduction (SR) is a training protocol aimed to stimulate lipolysis locally, even though this training protocol has not been extensively studied in recent years. Thus, the present study sought to investigate the effect of a circuit-training SR on subcutaneous adipose tissue in healthy adults.
Methods:
Fourteen volunteers were randomly assigned to spot reduction (SR) or to a traditional resistance training (RT) protocol. Body composition via bioimpedance analysis (BIA) and subcutaneous adipose tissue via skinfold and ultrasound were measured before and after eight weeks of training.
Results:
SR significantly reduced body mass (p < 0.05) and subcutaneous abdominal adipose tissue (p < 0.05).
Conclusions:
circuit-training SR may be an efficient strategy to reduce in a localized manner abdominal subcutaneous fat tissue depot.
... Recently, the effect of priming exercise, that is exercise which is meant to activate metabolic processes prior to the real exercise, has been attributed to an enhanced microvascular oxygen (O 2 ) distribution (Murias et al., 2011) by improved capillary perfusion (DeLorey et al., 2004). Capillary perfusion has been outlined as a determinant for fatty acid metabolism (Stallknecht et al., 2007;Laaksonen et al., 2013). Because fatty acid oxidation is restricted during exercise at high intensities (Romijn et al., 1993), it is likely that mechanisms causing oxidative adaptations in terms of fatty acid oxidation take effect in the resting interval of an interval training session and profit from the elevated microvascular perfusion. ...
... This increases the capillary surface area (Pittman, 2000), which facilitates local gas exchange. Further, recent studies reported that a higher local muscle perfusion is associated with an enhanced oxidative metabolism like fatty acid oxidation (Romijn et al., 1993;Horowitz, 2003;Stallknecht et al., 2007;Laaksonen et al., 2013). Consequently, especially fatty acid oxidation could be enhanced by improved post-exercise O 2 availability during the early recovery phase or, with regard to interval training, during the low interval. ...
Increased local blood supply is thought to be one of the mechanisms underlying oxidative adaptations to interval training regimes. The relationship of exercise intensity with local blood supply and oxygen availability has not been sufficiently evaluated yet. The aim of this study was to examine the effect of six different intensities (40-90% peak oxygen uptake, VO2peak ) on relative changes in oxygenated, deoxygenated and total haemoglobin (ΔO2 Hb, ΔHHb, ΔTHb) concentration after exercise as well as end-exercise ΔHHb/ΔVO2 as a marker for microvascular O2 distribution. Seventeen male subjects performed an experimental protocol consisting of 3 min cycling bouts at each exercise intensity in randomized order, separated by 5 min rests. ΔO2 Hb and ΔHHb were monitored with near-infrared spectroscopy of the vastus lateralis muscle, and VO2 was assessed. ΔHHb/ΔVO2 increased significantly from 40% to 60% VO2 peak and decreased from 60% to 90% VO2 peak. Post-exercise ΔTHb and ΔO2 Hb showed an overshoot in relation to pre-exercise values, which was equal after 40-60% VO2peak and rose significantly thereafter. A plateau was reached following exercise at ≥80% VO2peak . The results suggest that there is an increasing mismatch of local O2 delivery and utilization during exercise up to 60% VO2peak . This insufficient local O2 distribution is progressively improved above that intensity. Further, exercise intensities of ≥80% VO2peak induce highest local post-exercise O2 availability. These effects are likely due to improved microvascular perfusion by enhanced vasodilation, which could be mediated by higher lactate production and the accompanying acidosis.
... The study was approved by the Ethics Committee for Medical Research in Copenhagen (KF 11-055/03). Descriptive data from the current study have been previously published in a separate paper with a different focus [16]. The subjects were regularly active training two or more times per week and using bicycling as their preferred mode of commuting transport in their daily life. ...
It is not clear if fat oxidation is attenuated at higher exercise intensities, when exercising with a small muscle mass, and therefore, we studied leg fat oxidation during graded one‐leg exercise. Ten males (age: 27 ± 2 years, body mass: 82 ± 3 kg, BMI: 24 ± 1 kg m⁻², V̇O2max: 49 ± 2 mL min⁻¹ kg⁻¹) performed one‐leg exercise at 25% of maximal workload (Wmax) for 30 min, followed by 120‐min exercise at 55% Wmax with the contralateral leg, and finally 30‐min exercise at 85% Wmax with the first leg. Blood was sampled from an artery and both femoral veins, and blood flow was determined using Doppler ultrasound. Muscle biopsies were obtained before and after 30 min at each workload. One‐way RM ANOVA was applied to determine the impact of exercise intensity. Data are expressed as mean ± SEM. From rest through exercise average blood flow (0.4 ± 0.1, 2.1 ± 0.1, 2.6 ± 0.2, 3.7 ± 0.2 L min⁻¹) and oxygen uptake across the leg (0.03 ± 0.01, 0.23 ± 0.02, 0.35 ± 0.03, 0.53 ± 0.04 L min⁻¹) increased with exercise intensity (p < 0.001). Leg RQ (0.76 ± 0.04, 0.86 ± 0.02,0.87 ± 0.01, 0.92 ± 0.01, p < 0.001), leg plasma FA uptake (2 ± 2, 46 ± 8,83 ± 9, 114 ± 16 μmol min⁻¹; p < 0.001) and rate of leg fat oxidation (0.016 ± 0.005, 0.062 ± 0.012, 0.075 ± 0.011, 0.084 ± 0.018 g min⁻¹, p < 0.007) increased with exercise intensity. Muscle‐free carnitine content was unchanged from rest at 25% Wmax and decreased after 30 min exercise at 55% and 85% Wmax (17.4 ± 1.6, 16.6 ± 0.7, 14.5 ± 1.2, 10.5 ± 1.0 mmol/kg dry muscle, respectively; p < 0.006). During incremental one‐leg exercise, the rate of leg fat oxidation was not attenuated with increasing exercise intensity, probably due to an insufficient muscle metabolic stress response.
... Adipose tissue is vascular and requires its share of perfusion (Rosell and Belfrage 1979); therefore, a higher amount of body fat could theoretically contribute to a higher BV. Blood flow to adipose tissue at rest has been reported to be approximately 20-30 mL/kg adipose tissue/min (∼5%-7% of cardiac output in normal weight individuals) and several times higher in adipose tissue adjacent to active muscles during exercise, but the relative perfusion rate is reduced with increasing body fatness to ∼15 mL/kg adipose tissue/min in individuals with body fat percentages >40% (Larsen et al. 1966;Lesser and Deutsch 1967;Rosell and Belfrage 1979;Stallknecht et al. 2007). We assessed the influence of fat mass on Hb mass and BV (Fig. 1) and found no relationship between these variables (Fig. 1), suggesting that adding fat mass or increasing body fat percentage does not increase Hb mass and BV. ...
Blood properties influence aerobic exercise performance. While vascular volumes and hemoglobin mass (Hbmass) are elevated in trained individuals, evidence of sex differences in vascular volumes is equivocal due to inadequate matching of aerobic fitness between males and females. This cross-sectional study aimed to compare hematological values normalized to body mass (BM) and fat-free mass (FFM) between males (n = 45) and females (n = 34) matched for aerobic fitness (V̇O2max) normalized to FFM (mL∙kg FFM⁻¹∙min⁻¹). Data included body composition measured by dual-energy X-ray absorptiometry (DXA), V̇O2max from an incremental test, and hematological values derived from a CO rebreathe test. Fat mass was unrelated to blood volume (BV; R² = 0.02, P = 0.26) and Hbmass (R2 = 0.03, P = 0.16), while FFM was the strongest predictor of both (R2 = 0.75 and R2 = 0.83, respectively, P < 0.001). Females exhibited higher FFM-normalized BV (+4%, P < 0.05) and plasma volume (PV) (+14%, P < 0.001) and lower red blood cell volume (RBCV) (−8%, P < 0.001) and Hbmass (−8%, P < 0.001) compared to males. Positive correlations between aerobic fitness and relative Hbmass and BV were observed in both sexes when normalized to BM and FFM (0.48 < r < 0.71; P < 0.003). Stepwise multiple regression models, including FFM, V̇O2max, height, and [Hb], provided accurate predictions of Hbmass (R2 = 0.91) and BV (R2 = 0.85). Overall, sex differences persist in relative Hbmass, BV, PV, and RBCV after matching of aerobic fitness, though relative BV and PV were greater in females. These findings suggest sex-specific strategies in oxygen delivery and/or extraction, and they underscore the importance of carefully selecting normalization practices when assessing sex-based differences in hematological variables.
... However, when comparing protocols leading to weight loss, study by Murphy et al. [27] showed that training intervention resulted in the twofold reduction of IMAT in comparison to that one caused by caloric restriction and also correlated with improvement of insulin sensitivity. Possible explanation of this stronger effect of exercise could be preferable utilization of lipids from IMAT while exercising [35]. We should also note that caloric restriction also often leads to the reduction of lean mass and muscle volume [36,37], not only fat. ...
... Other studies on other possible applications, such as fat apoptosis and pelvic floor stimulation, are also ongoing [21]. Current data suggest that the physiological mechanism underlying magnetic stimulation is based on contractions that trigger intensive lipolysis within fat cells, leading to a large release of free fatty acids that damage the surrounding adipose tissue [22]. Damage to adipocytes causes apoptosis, as demonstrated in a study in which a 91.7% increase in the apoptotic ratio was observed in many histological samples [23]. ...
Background and Objective: In recent years, a strong desire for slimmer and healthier-looking bodies has grown in the population. The aim of this study was to evaluate the effectiveness and safeness of the new technology Flat Magnetic Stimulation for buttock and abdomen remodeling in athletic subjects. Methods: A total of 49 patients (31 females and 18 males) were enrolled. Patients’ digital photos and buttocks/abdomen circumference measurements were taken to assess and monitor the effectiveness of treatment on muscle firming. The level of patient satisfaction was evaluated by a questionnaire based on a seven point Likert scale. Average scores were calculated at a 1-month follow-up (FU). Results: A significant increase in the buttocks’ mean circumference from 85.5 ± 0.7 cm to 88.5 ± 0.7 cm (p < 0.05) and in the abdomens’ mean circumference from 76.5 ± 9.19 cm to 78 ± 9.89 cm (p < 0.05) was observed 1 month after the last treatment. All subjects reported that their buttocks and abdomens felt more lift and toned. The average abdomen and buttocks satisfaction scores improve significantly at 1-month FU. Conclusions: Our data show that FMS treatment could be used as an effective mechanism for muscle toning.
... This phenomenon is mirrored in adipose tissue because acute exercise increases ATBF in specific fat deposits that are close to working muscle. 61,62 Cycling exercises did not increase blood ...
Although the hallmark of obesity is the expansion of adipose tissue, not all adipose tissue expansion is the same. Expansion of healthy adipose tissue is accompanied by adequate capillary angiogenesis and mitochondria-centered metabolic integrity, whereas expansion of unhealthy adipose tissue is associated with capillary rarefaction and mitochondrial derangement, resulting in deposition of immune cells (M1-stage macrophages) and excess production of pro-inflammatory cytokines. Accumulation of these dysfunctional adipose tissues has been linked to the development of obesity comorbidities, such as type 2 diabetes, hypertension, dyslipidemia, and cardiovascular disease, which are leading causes of human mortality and morbidity in modern society. Mechanistically, vascular rarefaction and mitochondrial incompetency (for example, low mitochondrial content, fragmented mitochondria, defective mitochondrial respiratory function, and excess production of mitochondrial reactive oxygen species) are frequently observed in adipose tissue of obese patients. Recent studies have demonstrated that exercise is a potent behavioral intervention for preventing and reducing obesity and other metabolic diseases. However, our understanding of potential cellular mechanisms of exercise, which promote healthy adipose tissue expansion, is at the beginning stage. In this review, we hypothesize that exercise can induce unique physiological stimuli that can alter angiogenesis and mitochondrial remodeling in adipose tissues and ultimately promote the development and progression of healthy adipogenesis. We summarize recent reports on how regular exercise can impose differential processes that lead to the formation of either healthy or unhealthy adipose tissue and discuss key knowledge gaps that warrant future research.
... In addition to muscle definition, HIFEM, therefore, metabolically influences adjacent fat tissue, which explains the improved body contour seen in this study. 13,14 Generally, cellulite results in dimpled-looking skin that commonly HIFEM clinical studies 2,3,20 showed that muscle growth occurs in the vast majority of treated patients. Corresponding findings were also noticed in this study. ...
Background:
High-intensity electromagnetic field procedure (HIFEM) is an effective tool for body shaping and muscle toning. Radiofrequency (RF) combined with targeted pressure energy (TPE) provides the solution for skin laxity and cellulite.
Aims:
To document the effect of consecutive use of HIFEM, RF, and TPE for treatment of abdomen and buttocks.
Methods:
Fifteen subjects (44.3 ± 14.2 years, 22.3 ± 2.3 kg/m2 ) finished treatments and consequent follow-ups. They were treated over the abdomen (Group 1, N = 7) or buttocks (Group 2, N = 8), receiving four treatment procedures consisting of HIFEM treatment administered first, immediately followed by the simultaneous RF & TPE treatment. Each session took approximately 50 min (30 min of HIFEM; up to 20 min of RF & TPE) depending on the treated area. Study outcomes were assessed by the circumference measurement, satisfaction and comfort questionnaires, and digital photographs.
Results:
Combined treatments were safe and comfortable. At 1 month, the abdominal circumference significantly decreased by 4.4 cm, while buttocks showed a significant increase by 1.0 cm. The abdomen (-4.1 cm) and buttocks (+1.2 cm) circumference results were sustained for three months without a significant decline. Satisfaction was high in both groups (93.3%) since most subjects noted that the appearance of the treated area has been improved, referring to both body sculpting and skin appearance.
Conclusions:
The consecutive application of HIFEM, RF, and TPE treatments noticeably improved the appearance of the abdomen and buttocks. Subjects showed enhancement of abdominal body contour, buttock lifting, and improved skin quality manifested by reduced skin laxity and cellulite.
... 62 Additionally, a "spot lipolysis" effect has been described consisting in the mobilization of fatty acids from subcutaneous adipose tissue surrounding active muscles during exercise. 63 Whether these fatty acids derive from intramyocellular (IMTG) or extramyocellular (IMAT) lipids compartments within muscle is unknown. The findings of our study suggest that exercise training may favor the utilization of lipids from IMAT. ...
Objective
The purpose of this study was to evaluate the effect of exercise training on ectopic fat within skeletal muscle (intermuscular adipose tissue [IMAT]) in adult populations with chronic diseases.
Methods
A literature search was conducted in relevant databases to identify randomized controlled trials (RCTs) from inception. Selected studies examined the effect of aerobic training (AET), resistance training (RT), or combined training (COM) on IMAT as assessed by noninvasive magnetic resonance (MRI) or computed tomography (CT). Eligibility was determined using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Data extraction was performed using the population (P), intervention (I), comparison (C), outcome (O), timing (T), and settings (S) approach. Methodological quality was analyzed by the Cochrane risk of bias assessment. Standardized effect sizes (ES) with 95% Cis were calculated. Heterogeneity among studies was quantified using I2 statistics. Subgroup and meta-regression analyses were included. Risk of publication bias was examined by the Egger regression test.
Results
Nineteen RCTs included 962 adults (628 women; age range = 34.8–93.4 y) with different chronic conditions that participated in 10 AET, 12 RT, and 5 COM interventions. The quality of studies was deemed moderate. Overall, the effect of exercise on IMAT was small (ES = 0.24; 95% CI = 0.10–0.37; heterogeneity I2 = 0.0%) compared with no exercise or control interventions. Moderate intensity AET and COM had larger ES compared with RT regardless of intensity. This effect was associated with exercise-induced body weight and fat mass losses. Subgroup analysis revealed larger ES in studies assessing IMAT by MRI compared with CT, in adults and middle-aged individuals compared with older adults, and in participants who were HIV+ compared with other diagnoses.
Conclusion
AET and COM of moderate intensity reduce IMAT in individuals from 18 to 65 years of age who are affected by chronic diseases. This effect is associated with exercise-induced body weight and fat mass losses. In older individuals who are frail and patients at an advanced disease stage, exercise may result in a paradoxical IMAT accumulation.
Impact
In people affected by chronic conditions, IMAT accumulation induces muscle mass and strength losses, decline in physical performance, inflammation, and metabolic alterations. The present study shows that moderate intensity AET or COM prevent or reduce IMAT in these conditions. Thus, the deleterious effect of IMAT on skeletal muscle homeostasis may be reverted by a properly prescribed exercise regime. Findings of the present systematic review are critical for physical therapists and health care professionals as they emphasize the therapeutic role of exercise and provide recommendations for exercise prescription that ultimately may have a positive impact on the course of disease, recovery of functionality, and independence.
Lay summary
Aerobic exercise (eg, walking/jogging, cycling) alone or combined with resistance exercise (strength training with free-weights, kettle bells, or gym equipment) is effective in reducing fat streaks that infiltrate muscles and impair muscle function and growth, particularly in adults affected by chronic diseases.
... During acute prolonged exercise, plasma FFA levels increase primarily due to increased adipose tissue blood flow and lipolysis [181,182], partly via adrenergic signaling [183,184], which is also elevated in the recovery period after exercise cessation [182,185] to support the increased fat oxidation by muscle in response to exercise (reviewed in [186]). While acute exercise causes a transient increase in plasma FFA levels, long-term ET enhances insulin sensitivity and increases vascularization of adipose tissue [187], that in turn potentiates insulin's inhibitory effect on lipolysis in response to for example a meal [188]. ...
Metabolic dysfunction is a comorbidity of many types of cancers. Disruption of glucose metabolism is of concern, as it is associated with higher cancer recurrence rates and reduced survival. Current evidence suggests many health benefits from exercise during and after cancer treatment, yet only a limited number of studies have addressed the effect of exercise on cancer-associated disruption of metabolism. In this review, we draw on studies in cells, rodents, and humans to describe the metabolic dysfunctions observed in cancer and the tissues involved. We discuss how the known effects of acute exercise and exercise training observed in healthy subjects could have a positive outcome on mechanisms in people with cancer, namely: insulin resistance, hyperlipidemia, mitochondrial dysfunction, inflammation, and cachexia. Finally, we compile the current limited knowledge of how exercise corrects metabolic control in cancer and identify unanswered questions for future research.
... Effects of retinoids and carotenoids on skeletal muscle mass and muscle-WAT interactions might be of special relevance to muscle performance during exercise. Moderate aerobic exercise increases WAT lipolysis to fuel the metabolic demands [217]; mechanisms for this adaptive response include local effects with selective activation of lipolysis in the fat depots closest to the active muscles [218], likely through the release of paracrine signals from the contracting muscles, such as irisin. Retinoids, as atRA, increase skeletal muscle relative mass [86], mitochondria content [56], fatty acid oxidation [56,215] and irisin se cretion [86], as well as fat mobilization in WAT [55]. ...
Antiobesity activities of carotenoids and carotenoid conversion products (CCPs) have been demonstrated in pre-clinical studies, and mechanisms behind have begun to be unveiled, thus suggesting these compounds may help obesity prevention and management. The antiobesity action of carotenoids and CCPs can be traced to effects in multiple tissues, notably the adipose tissues. Key aspects of the biology of adipose tissues appear to be affected by carotenoid and CCPs, including adipogenesis, metabolic capacities for energy storage, release and inefficient oxidation, secretory function, and modulation of oxidative stress and inflammatory pathways. Here, we review the connections of carotenoids and CCPs with adipose tissue biology and obesity as revealed by cell and animal intervention studies, studies addressing the role of endogenous retinoid metabolism, and human epidemiological and intervention studies. We also consider human genetic variability influencing carotenoid and vitamin A metabolism, particularly in adipose tissues, as a potentially relevant aspect towards personalization of dietary recommendations to prevent or manage obesity and optimize metabolic health. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.
... We hypothesize that the induced supramaximal contractions may lead to an increased metabolic activity in the region of stimulation and subsequent breakdown of lipids into free fatty acids (FFA) and glycerol [8,[11][12][13] as seen during intensive resistance training [14,15]. In the case of supramaximal contractions, the lipid breakdown could lead to overflow of free fatty acids (FFA) in the intracellular space. ...
Objectives
While controlled thermal changes in subcutaneous tissue have been used to trigger apoptosis of fat cells and have been proven clinically efficacious, another mechanism of electromagnetic stress suggests that fat apoptosis could be achieved by a non‐thermal manner as well. This animal model study investigates the use of a non‐invasive high‐intensity magnetic field device to induce apoptosis in fat cells.
Methods
Yorkshire pigs (N = 2) received one treatment (30 minutes) in the abdominal area using a High‐Intensity Focused Electromagnetic (HIFEM) device. Punch biopsy samples of fat tissue and blood samples were collected at the baseline, 1 and 8 hours after the treatment. Biopsy samples were sectioned and evaluated for the levels of an apoptotic index (AI) by the TUNEL method. Statistical significance was examined using the rANOVA and Tukey's test (α 5%). Biopsy samples were also assessed for molecular biomarkers. Blood samples were evaluated to determine changes related to fat and muscle metabolism. Free fatty acids (FFA), triacylglycerol (TG), glycerol and glucose (Glu) were used as the main biomarkers of fat metabolism. Creatinine, creatinine kinase (CK), lactate dehydrogenase (LDH) and interleukin 6 (IL6) served as the main biomarkers to evaluate muscle metabolism.
Results
In treated pigs, a statistically significant increase in the apoptotic index (AI) (P = 1.17E‐4) was observed. A significant difference was found between AI at baseline (AI = 18.75%) and 8‐hours post‐treatment (AI = 35.95%). Serum levels of fat and muscle metabolism indicated trends (FFA −0.32 mmol · l⁻¹, −28.1%; TG −0.24 mmol · l⁻¹, −51.8%; Glycerol −5.68 mg · l⁻¹, −54.8%; CK +67.58 μkat · l⁻¹, +227.8%; LDH +4.9 μkat · l⁻¹,+35.4%) suggesting that both adipose and muscle tissue were affected by HIFEM treatment. No adverse events were noted to skin and surrounding tissue.
Conclusions
Application of a high‐intensity electromagnetic field in a porcine model results in adipocyte apoptosis. The analysis of serum levels suggests that HIFEM treatment influences fat and muscle metabolism. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.
... Research on high intensity muscle training has shown that a lipolytic reaction takes plan in fat tissue adjacent to the contracting muscle [20]. The MRI scans presented herein show a reduction in adipose tissue not immediately after the treatments, but 2 months after the last procedure. ...
Objectives
This study introduces an initial evaluation of a novel High‐Intensity Focused Electromagnetic (HIFEM) technology. The primary goal is to quantify any effects the treatments may have on abdominal tissues, as well as to establish hypotheses for future research of this technology.
Methods
Twenty‐two patients received four abdominal treatments using the EMSCULPT device (BTL Industries Inc., Boston, MA). Anthropometric evaluations were recorded and digital photographs were taken at baseline, at 2 months, and at 6 months post‐treatments. The MRI without contrast determined by vertertebras T12 and S1 (FIESTA and FSPRG sequences) was used to measure dimensions in coronal cross‐sectional images of abdominal muscle and fatty tissues, in order to assess any anatomical changes induced by the application.
Results
Analysis of the same MRI slices verified by tissue artefacts showed a statistically significant (all P < 0.0001) average 18.6% reduction of adipose tissue thickness, 15.4% increase in rectus abdominis muscle thickness, and 10.4% reduction in rectus abdominus separation (diastasis recti) as measured from the medial border of the muscle 2 months post‐treatment. More significant improvements were observed in patients with BMI 18.5–24.9 (classified as “normal”). MRI data from 6‐month follow‐up suggest the changes can be preserved in longer term. Tape measurements showed on average 3.8 cm subumbilical circumference reduction. The weight of the subjects did not change significantly (average −0.5 lb; P > 0.05). No adverse events were reported.
Conclusions
MRI, considered as a highly precise diagnostic method, revealed simultaneous muscle growth, fat reduction and reduced abdominal separation at 2 months and at 6 months post treatments, unrelated with dieting. Further research should investigate the exact physiological processes which stand behind the tissue changes observed in this study. Lasers Surg. Med. © 2018 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.
... Characteristics of the subjects are given in Table 1. This study and the basal data of the included subjects have been used for a prior publication with a different focus (Stallknecht et al. 2007). Prior to the experiment, subjects were accustomed to exercise on the knee extension ergometer and maximal work capacity (W max ) was determined for each leg as described by Andersen and Saltin (1985). ...
Purpose
Sphingosine-1-phosphate (S1P) regulates cardiovascular function and plays an important role in muscle biology. We have previously reported that cycling exercise increased plasma S1P. Here, we investigated the effect of exercise duration and intensity on plasma and skeletal muscle S1P levels.
Methods
In the first experiment, 13 male athletes performed a 60-min exercise at 65 % of VO2max and a graded exercise until exhaustion on a rowing ergometer. Samples of the venous blood were taken, and plasma, erythrocytes and platelets were isolated. In the second experiment, ten male moderately active subjects performed three consecutive periods of one-leg knee extension exercise (at 25, 55 and 85 % of the maximal workload). Muscle biopsies and blood samples from the radial artery and femoral veins were taken.
Results
Under basal conditions, S1P was released from the leg, as its concentration was lower in the arterial than in the venous plasma (p
... Olsen and Edelstein (30) found a decrease in skinfold thickness of the trained arm compared to the untrained arm. The local fat reduction was supported in another, more recent study (31) where male subjects perform single-leg extensions with light weight for 30 consecutive minutes. An increase in blood flow and lipolysis were observed in the exercising leg when compared to the resting leg. ...
It is well documented that resistance exercise can be performed by patients with breast cancer-related arm lymphedema. The aim of this pilot study was to evaluate the feasibility and safety of a 12-week self-administered weight lifting program for arm and shoulder, and its influence on arm lymphedema status, upper extremity muscle strength, and disability. Twenty-three patients with breast cancer-related arm lymphedema performed the program 3 times/week. The weight resistance levels were individually adjusted for shoulder flexion and adduction, and elbow extension and flexion corresponding to a repetition range of 8-12 repetition maximum. A log book was used to evaluate adherence to the program, wearing of compression sleeve and perceived exertion. Measurements were performed before a 2-week control period without intervention, and before and after intervention, and with arm volume measurements every fortnight to check for adverse events. Results revealed no significant changes during the control period. Adherence to the intervention program was excellent, and two adverse events were registered during the first weeks. After intervention, an increase of shoulder and arm strength (measured by an isometric muscle strength device) was found in all exercises (p = 0.001-0.003). A reduction of excess volume was shown, in ml (p = 0.03) and percentage (p = 0.005), measured by water displacement method. A tendency towards reduction (p = 0.07) of fat tissue in the upper arm (n = 10) in both arms was found measured by MRI. In this pilot study, we concluded that a home-based weight-lifting program performed by patients with breast cancer-related arm lymphedema is feasible and safe providing that the program includes regular follow-up for safety.
... After resting for at least 1 h, the subject was positioned in a two-legged knee-extension ergometer in a semisupine position. The ergometer is a modified version of the one-legged knee extension ergometer (Andersen et al. 1985), which has been used previously (Stallknecht et al. 2007). Subsequently, at rest, blood was sampled simultaneously from the brachial artery and femoral veins at −15 min and immediately before exercise. ...
New Findings
What is the central question of this study?
Does physical inactivity influence the exercise‐induced release of tumour necrosis factor‐α and interleukin‐6 in healthy humans? In young, healthy subjects, we immobilized one leg for 2 weeks, followed by 45 min two‐legged exercise where one leg served as the control and the other was the previously inactive leg.
What is the main finding and its importance?
We found that prior physical inactivity enhances interleukin‐6 release during exercise, and it is released in the blood from the legs during exercise much faster than previously known. However, tumour necrosis factor‐α is not released in the blood with exercise, even from a previously inactive leg.
Data on interleukin‐6 (IL‐6) and tumour necrosis factor‐α (TNF‐α) release during acute exercise are not conclusive, and information is lacking about the impact of physical inactivity. Some studies have shown an increase, but others report no changes in IL‐6 and TNF‐α release during exercise. We have now studied the temporal relationship of leg IL‐6 and TNF‐α release before and during isolated two‐legged exercise after 14 days of one‐leg immobilization (IM) while the other leg served as the control (CON) leg. Fifteen healthy male subjects (mean ± SEM age, 23 ± 1 years; body mass index, 23.6 ± 0.7 kg m ⁻² ; and maximal oxygen uptake, 46.8 ± 1.4 ml kg ⁻¹ min ⁻¹ ) performed 45 min of two‐legged dynamic knee‐extensor exercise at 19.6 ± 0.8 W. Arterial and femoral venous blood samples from the CON and the IM leg were collected every 15 min during exercise, and leg blood flow was measured with Doppler ultrasound. The arterial plasma IL‐6 concentration increased ( P < 0.05) with exercise (rest, 1.3 ± 0.1 pg ml ⁻¹ ; 15 min, 1.9 ± 0.2 pg ml ⁻¹ ; 30 min, 2.4 ± 0.2 pg ml ⁻¹ ; and 45 min, 3.1 ± 0.3 pg ml ⁻¹ ). Interleukin‐6 release occurred after 15 min of exercise, and the release from the IM leg was significantly greater compared with the CON leg after 45 min (1114 ± 152 versus 606 ± 14 pg min ⁻¹ , respectively, P < 0.05). Tumour necrosis factor‐α release did not differ between the CON and the IM leg, and arterial concentrations remained unchanged during exercise ( P > 0.05). In conclusion, prior immobilization enhances release of IL‐6 from the leg during exercise at a moderate workload, and the release is already present in the early phase of exercise. Neither immobilization nor exercise had an effect on TNF‐α release in the working legs.
Background
Electromagnetic treatments have recently been combined with radiofrequency to reduce the fat layer and simultaneously increase muscle thickness. Studies report treatment efficacy, using photographs and imaging methods.
Methods
A literature review was conducted. Measurement data were tabulated. The EmSculpt Neo device (BTL Industries, Boston, MA) was used in all studies.
Results
Seven studies evaluated the fat thickness and muscle thickness using either ultrasound (1 study) or magnetic resonance imaging methods (6 studies). The abdomen was treated in 2 studies. The other studies treated the lateral thighs, flanks, buttocks, inner thighs, and upper arms. The mean reduction in fat thickness was 8.0 mm, and the mean increase in muscle thickness was 5.5 mm. All 7 studies were authored by BTL medical advisors. Measured changes were likely within the margin of error and of questionable clinical relevance. Few adverse events were reported.
Discussion
Photographs were frequently not standardized, showing changes in treated areas, but unexplained changes in nontreated areas as well. The magnetic resonance imaging scans were affected by differing levels of the axial slice. Measured changes were incremental and likely not indicative of a true treatment effect. The scientific basis for efficacy is tenuous, both for fat reduction and muscle hypertrophy.
Conclusions
A scientific evaluation of the results fails to produce reliable evidence of a clinically meaningful result for this combination energy-based treatment. Financial conflict is a major factor. Liposuction remains the gold standard.
Background
The spread of non-invasive procedures for fat deposits removal has increased rapidly in recent years. In the field of esthetic medicine, high-intensity focused electromagnetic field (HIFEM) technology has recently been introduced, as a tool for toning and strengthening muscles, which goes far beyond normal physical exercise.
Objective
The purpose of this study is to evaluate the efficacy and safety of a new device for body remodeling.
Methods
A set of 15 patients (7 males and 8 females, BMI 24.05 ± 2.01 kg m⁻², age 32–57) participated in this study. Patients were enrolled at Dermatos center, Montesilvano, Abruzzo, Italy. The technology used is FMS (Flat Magnetic Stimulation): 6–8 treatment sessions were performed. The sessions must be repeated twice a week, with a minimum of 2 days between each session. Treatment duration varies from 20 to 45 min, depending on patients.
Results
During 1-month follow-up after the last treatment evaluations, the results showed tonification, the strengthening of muscles, and the reduction of localized adiposity. There is a significant reduction in waist circumference (80.7 ± 4.3 cm vs 77.3 ± 5.6 cm, p < 0.001). All patients showed relatively high satisfaction immediately after the last treatment.
Conclusions
Our data show that intense muscle activity is generated by FMS treatments, suggesting that this technology could be used as a convenient and effective muscle toning tool.
Over the years the problem of spot reduction has often been addressed. Many fats regions tend to resist weight loss compared to others that have a greater vascularization; scientific evidence shows that blood flow in adipose areas is not high enough to allow the release of all fatty acids into the circulation. The objective of this essay is to prove how an adequate pre-workout muscle vascularization can have positive effects on the reduction of adipose tissue in less vascularized areas both in terms of time and effectiveness. Ten subjects will be examined divided into two groups (control group and experimental group) for the duration of twelve weeks, the experimental group will perform a pre-vascularization of the muscle district closest to the area of the adipose tissue taken under consideration, the control group instead, will skip this pre-vascularization phase. The progress of the two groups will be monitored until the end of the period under examination through anthropometric and plicometric tests. The expected results should confirm that adequate vascularization before training of the experimental group led to a greater and anticipated reduction of localized adipose tissue compared to the subjects of the control group who did not perform this method.
The field of non-invasive body shaping has long been represented solely by fat reducing technologies, and the condition of the underlying muscles could be altered only by physical exercise. In 2018, high-intensity focused electromagnetic (HIFEM) technology was introduced to simultaneously tone and strengthen muscle and reduce fat. The technology is based on delivering focused electromagnetic fields into the treatment area, causing supramaximal muscle contractions. Clinical studies showed a significant reduction in subcutaneous white adipose tissue (sWAT) and an increase in muscle thickness (e.g., abdominal muscle) after a series of HIFEM treatments. The effect on both types of tissue was also confirmed by histological studies and was present in all imaging techniques (ultrasonography, magnetic resonance imaging, computed tomography). With an effect of this kind, HIFEM technology has opened up a completely new segment in body contouring.
Non‐invasive body contouring is a rapidly growing field in cosmetic dermatology. Non‐invasive contouring devices improve the body's appearance through the removal of excess adipose tissue, particularly in areas in which fat persists despite optimal diet and exercise routine. The technology can also be used for skin tightening. This article reviews the five FDA‐approved non‐invasive body contouring modalities: cryolipolysis, laser, high‐intensity focused electromagnetic field, radiofrequency and high‐intensity focused ultrasound. These devices have emerged as a popular alternative to surgical body contouring due to their efficacy, favourable safety profile, minimal recovery time and reduced cost. Although they do not achieve the same results as liposuction, they are an attractive alternative for patients who do not want the risks or costs associated with surgery. When used appropriately and correctly, these devices have demonstrated excellent clinical efficacy and safety.
Работа посвящена изучению и обобщению научных данных о возможности частично воздействовать на толщину подкожной жировой клетчатки с помощью локальных упражнений на соответствующие части тела. Сделана попытка отделить друг от друга понятия «липолиз» и «жиросжигание». Сделан вывод о невозможности устойчивого локального уменьшения толщины подкожной жировой клетчатки с помощью упражнений локального характера на соответствующие части тела.
Aim:
To determine the genomic mechanisms by which adipose tissue responds to acute and chronic exercise.
Methods:
We profiled the transcriptomic and epigenetic response to acute exercise in human adipose tissue collected before and after endurance training.
Results:
Although acute exercises were performed at same relative intensities, the magnitude of transcriptomic changes after acute exercise was reduced by endurance training. DNA methylation remodeling induced by acute exercise was more prominent in trained versus untrained state. We found an overlap between gene expression and DNA methylation changes after acute exercise for 32 genes pre-training and six post-training, notably at adipocyte-specific genes.
Conclusion:
Training status differentially affects the epigenetic and transcriptomic response to acute exercise in human adipose tissue.
Metabolic flexibility is the ability to respond or adapt to conditional changes in metabolic demand. This broad concept has been propagated to explain insulin resistance and mechanisms governing fuel selection between glucose and fatty acids, highlighting the metabolic inflexibility of obesity and type 2 diabetes. In parallel, contemporary exercise physiology research has helped to identify potential mechanisms underlying altered fuel metabolism in obesity and diabetes. Advances in “omics” technologies have further stimulated additional basic and clinical-translational research to further interrogate mechanisms for improved metabolic flexibility in skeletal muscle and adipose tissue with the goal of preventing and treating metabolic disease.
Blood flow (BF) in exercising muscles is an important factor for exercise capacity. Recently, a non-invasive method to estimate capillary BF (Qcap ) was introduced. Using this method, the Fick principle is re-arranged by using relative differences in deoxygenated haemoglobin (ΔHHb) as a surrogate for arteriovenous O2 difference and pulmonary oxygen uptake (VO2 ) instead of muscular oxygen uptake. The aim of this study was to examine (I) the relationship between Qcap and exercise intensity during and following exercise, and (II) to critically reflect the Qcap approach. Seventeen male subjects completed six bouts of cycling exercise with different exercise intensities (40-90% peak oxygen uptake, VO2peak ) in randomized order. VO2 and ΔHHb were monitored continuously during the trail. Qcap was modelled bi-exponentially, and mean response time (MRT) was calculated during recovery as well as the dissociation of modelled VO2 and Qcap recovery kinetics (MRT/τVO2 ). End-exercise Qcap increased continuously with exercise intensity. This also applied to MRT. Postexercise MRT/τVO2 increased from 40 to 60% VO2peak but remained stable thereafter. The results show that Qcap response to exercise is linearly related to exercise intensity. This is presumably due to vasoactive factors like shear-stress or endothelial-mediated vasodilation. MRT/τVO2 shows that postexercise Qcap is elevated for a longer period than VO2 , which is representative for metabolic demand following exercise ≥70% VO2peak . This is a hint for prolonged local vasodilation. According to previous studies, Qcap could not be modelled properly in some cases, which is a limitation to the method and therefore has to be interpreted with caution.
Adipose tissue is a major source of nonesterified fatty acids, which are involved in the etiopathogenesis of several metabolic diseases. Mechanisms regulating the processes of lipolysis are of major importance because they represent potential drug targets. Physical exercise is a cost-effective prevention strategy and important therapy for civilization diseases and is an important physiological stimulus of lipolysis in adipose tissue. Besides the traditional role of catecholamines in the regulation of lipolysis, other recently described lipolytic factors, for example, atrial natriuretic peptide and IL-6, are discussed in the context of lipolysis. in vitro as well as in vivo studies provide a substantial amount of data, which are sometimes contradictory. Exercise modifies the functional balance between β and α adrenergic receptors, increases atrial natriuretic peptide-induced lipolysis and improves sensitivity of adipose tissue to insulin. Actual lipolytic rate is the summary of these complex interactions.
Fat cell lipolysis, the cleavage of triglycerides and release of fatty acids and glycerol, evolved to enable survival during prolonged food deprivation but is paradoxically increased in obesity, in which a surfeit of all energy metabolites is found. Essential, previously-unsuspected components have been discovered in the lipolytic machinery, at the protective interface of the lipid droplet surface and in the signaling pathways that control lipolysis. At least two adipocyte lipases are important for controlling lipolysis, hormone-sensitive lipase (HSL) and adipocyte triglyceride lipase (ATGL). Perilipin (PLIN) and possibly other proteins of the lipid droplet surface are master regulators of lipolysis, protecting or exposing the triglyceride core of the droplet to lipases. The prototypes for hormonal lipolytic control are beta adrenergic stimulation and suppression by insulin, both of which affect cyclic AMP levels and hence the protein kinase A-mediated phosphorylation of HSL and PLIN. Newly-recognized mediators of lipolysis include atrial natriuretic peptide, cyclic GMP, the ketone body 3-hydroxybutyrate, AMP kinase and mitogen-activated kinases. Lipolysis must be interpreted in its physiological context since similar rates of basal or stimulated lipolysis occur under different conditions and by different mechanisms. Age, sex, anatomical site, genotype and species differences are each important variables. Manipulation of lipolysis has therapeutic potential in several inborn errors and in the metabolic syndrome that frequently complicates obesity.
The purpose of this study was to investigate the effect of acute resistance exercise (RE) on lipolysis within adipose tissue and subsequent substrate oxidation to better understand how RE may contribute to improvements in body composition. Lipolysis and blood flow were measured in abdominal subcutaneous adipose tissue via microdialysis before, during, and for 5 h following whole body RE as well as on a nonexercise control day (C) in eight young (24 +/- 0.7 yr), active (>3 RE session/wk for at least 2 yr) male participants. Fat oxidation was measured immediately before and after RE via indirect calorimetry for 45 min. Dialysate glycerol concentration (an index of lipolysis) was higher during (RE: 200.4 +/- 38.6 vs. C: 112.4 +/- 13.1 micromol/l, 78% difference; P = 0.02) and immediately following RE (RE: 184 +/- 41 vs. C: 105 + 14.6 micromol/l, 75% difference; P = 0.03) compared with the same time period on the C day. Energy expenditure was elevated in the 45 min after RE compared with the same time period on the C day (RE: 104.4 +/- 6.0 vs. C: 94.5 +/- 4.0 kcal/h, 10.5% difference; P = 0.03). Respiratory exchange ratio was lower (RE: 0.71 +/- 0.004 vs. C: 0.85 +/- .03, 16.5% difference; P = 0.004) and fat oxidation was higher (RE: 10.2 +/- 0.8 vs. C: 5.0 +/- 1.0 g/h, 105% difference; P = 0.004) following RE compared with the same time period on the C day. Therefore, the mechanism behind RE contributing to improved body composition is in part due to enhanced abdominal subcutaneous adipose tissue lipolysis and improved whole body fat oxidation and energy expenditure in response to RE.
We combined tracer and arteriovenous (a-v) balance techniques to evaluate the effects of exercise and endurance training on leg triacylglyceride turnover as assessed by glycerol exchange. Measurements on an exercising leg were taken to be a surrogate for working skeletal muscle. Eight men completed 9 wk of endurance training [5 days/wk, 1 h/day, 75% peak oxygen consumption (Vo(2peak))], with leg glycerol turnover determined during two pretraining trials [45 and 65% Vo(2peak) (45% Pre and 65% Pre, respectively)] and two posttraining trials [65% of pretraining Vo(2peak) (ABT) and 65% of posttraining Vo(2peak) (RLT)] using [(2)H(5)]glycerol infusion, femoral a-v sampling, and measurement of leg blood flow. Endurance training increased Vo(2peak) by 15% (45.2 +/- 1.2 to 52.0 +/- 1.8 mlxkg(-1)xmin(-1), P < 0.05). At rest, there was tracer-measured leg glycerol uptake (41 +/- 8 and 52 +/- 15 micromol/min for pre- and posttraining, respectively) even in the presence of small, but significant, net leg glycerol release (-68 +/- 19 and -50 +/- 13 micromol/min, respectively; P < 0.05 vs. zero). Furthermore, while there was no significant net leg glycerol exchange during any of the exercise bouts, there was substantial tracer-measured leg glycerol turnover during exercise (i.e., simultaneous leg muscle uptake and leg release) (uptake, release: 45% Pre, 194 +/- 41, 214 +/- 33; 65% Pre, 217 +/- 79, 201 +/- 84; ABT, 275 +/- 76, 312 +/- 87; RLT, 282 +/- 83, 424 +/- 75 micromol/min; all P < 0.05 vs. corresponding rest). Leg glycerol turnover was unaffected by exercise intensity or endurance training. In summary, simultaneous leg glycerol uptake and release (indicative of leg triacylglyceride turnover) occurs despite small or negligible net leg glycerol exchange, and furthermore, leg glycerol turnover can be substantially augmented during exercise.
To determine if physical training conserves fat-free mass (FFM) in overweight men or women during weight loss.
Journals published between 1966 and 1993 were searched by MEDLINE and by handsearch to obtain all reports on human subjects in which the effect of exercise on body composition was studied in at least two concurrent treatment groups, of which at least one group did, and one group did not, undergo an exercise programme designed to promote fat loss. The relation between loss of weight, and loss of FFM, was examined by linear regression analysis among exercising and non-exercising groups of men or women.
Twenty-eight publications reported results on 226 sedentary men in 13 groups, 233 exercising men in 14 groups, 199 sedentary women in 23 groups, and 258 exercising women in 28 groups.
Aerobic exercise without dietary restriction among men caused a weight loss of 3 kg in 30 weeks compared with sedentary controls, and 1.4 kg in 12 weeks among women, but there was little effect on FFM. Resistance exercise had little effect on weight loss, but increased FFM by about 2 kg in men and 1 kg in women. Regression analysis shows that for a weight loss of 10 kg by diet alone the expected loss of FFM is 2.9 kg in men and 2.2 kg in women. When similar weight loss is achieved by exercise combined with dietary restriction the expected loss of FFM is reduced to 1.7 kg in men, and women. It is probable that the FFM conserved by exercise during weight loss contains more water and potassium than average FFM. The subjects studied were not severely obese.
Aerobic exercise causes a modest loss in weight without dieting. Exercise provides some conservation of FFM during weight loss by dieting, probably in part by maintaining glycogen and water.
The independent effects of diet- or exercise-induced weight loss on the reduction of obesity and related comorbid conditions are not known. The effects of exercise without weight loss on fat distribution and other risk factors are also unclear.
To determine the effects of equivalent diet- or exercise-induced weight loss and exercise without weight loss on subcutaneous fat, visceral fat skeletal muscle mass, and insulin sensitivity in obese men.
Randomized, controlled trial.
University research center.
52 obese men (mean body mass index [+/-SD], 31.3 +/- 2.0 kg/m2) with a mean waist circumference of 110.1 +/- 5.8 cm.
Participants were randomly assigned to one of four study groups (diet-induced weight loss, exercise-induced weight loss, exercise without weight loss, and control) and were observed for 3 months.
Change in total, subcutaneous, and visceral fat; skeletal muscle mass; cardiovascular fitness; glucose tolerance and insulin sensitivity.
Body weight decreased by 7.5 kg (8%) in both weight loss groups and did not change in the exercise without weight loss and control groups. Compared with controls, cardiovascular fitness (peak oxygen uptake) in the exercise groups improved by approximately 16% (P < 0.01). Although total fat decreased in both weight loss groups (P < 0.001), the average reduction was 1.3 kg (95% CI, 0.3 to 2.3 kg) greater in the exercise-induced weight loss group than in the diet-induced weight loss group (P = 0.03). Similar reductions in abdominal subcutaneous, visceral, and visceral fat-to-subcutaneous fat ratios were observed in the weight loss groups (P < 0.001). Abdominal and visceral fat also decreased in the exercise without weight loss group (P = 0.001). Plasma glucose and insulin values (fasting and oral glucose challenge) did not change in the treatment groups compared with controls (P = 0.10 for all comparisons). Average improvement in glucose disposal was similar in the diet-induced weight loss group (5.6 mg/kg skeletal muscle per minute) and in the exercise-induced weight loss group (7.2 mg/kg skeletal muscle per minute) (P > 0.2). However, these values were significantly greater than those in the control and exercise without weight loss groups (P < 0.001).
Weight loss induced by increased daily physical activity without caloric restriction substantially reduces obesity (particularly abdominal obesity) and insulin resistance in men. Exercise without weight loss reduces abdominal fat and prevents further weight gain.
This review was undertaken to determine whether exercise-induced weight loss was associated with corresponding reductions in total, abdominal, and visceral fat in a dose-response manner.
A literature search (MEDLINE, 1966--2000) was performed using appropriate keywords to identify studies that consider the influence of exercise-induced weight loss on total and/or abdominal fat. The reference lists of those studies identified were cross-referenced for additional studies.
Total fat. Review of available evidence suggested that studies evaluating the utility of physical activity as a means of obesity reduction could be subdivided into two categories based on study duration. Short-term studies (< or = 16 wk, N = 20) were characterized by exercise programs that increased energy expenditure by values double (2200 vs 1100 kcal.wk-1) that of long-term studies (> or = 26 wk, N = 11). Accordingly, short-term studies report reductions in body weight (-0.18 vs -0.06 kg x wk(-1)) and total fat (-0.21 vs -0.06 kg x wk(-1)) that are threefold higher than those reported in long-term studies. Moreover, with respect to dose-response issues, the evidence from short-term studies suggest that exercise-induced weight loss is positively related to reductions in total fat in a dose-response manner. No such relationship was observed when the results from long-term studies were examined. Abdominal fat. Limited evidence suggests that exercise-induced weight loss is associated with reductions in abdominal obesity as measured by waist circumference or imaging methods; however, at present there is insufficient evidence to determine a dose-response relationship between physical activity, and abdominal or visceral fat.
In response to well-controlled, short-term trials, increasing physical activity expressed as energy expended per week is positively related to reductions in total adiposity in a dose-response manner. Although physical activity is associated with reduction in abdominal and visceral fat, there is insufficient evidence to determine a dose-response relationship.
Background: The independent effects of diet- or exercise-induced weight loss on the reduction of obesity and related comorbid conditions are not known. The effects of exercise without weight loss on fat distribution and other risk factors are also unclear. Objective: To determine the effects of equivalent diet- or exercise-induced weight loss and exercise without weight loss on subcutaneous fat, visceral fat, skeletal muscle mass, and insulin sensitivity in obese men. Design Randomized, controlled trial. Setting: University research center. Participants: 52 obese men (mean body mass index [±SD], 31.3 ± 2.0 kg/m 2 ) with a mean waist circumference of 110.1 ± 5.8 cm. Intervention: Participants were randomly assigned to one of four study groups (diet-induced weight loss, exercise-induced weight loss, exercise without weight loss, and control) and were observed for 3 months. Measurements: Change in total, subcutaneous, and visceral fat; skeletal muscle mass; cardiovascular fitness; glucose tolerance and insulin sensitivity. Results: Body weight decreased by 7.5 kg (8%) in both weight loss groups and did not change in the exercise without weight loss and control groups. Compared with controls, cardiovascular fitness (peak oxygen uptake) in the exercise groups improved by approximately 16% (P 0.2). However, these values were significantly greater than those in the control and exercise without weight loss groups (P < 0.001). Conclusions: Weight loss induced by increased daily physical activity without caloric restriction substantially reduces obesity (particularly abdominal obesity) and insulin resistance in men. Exercise without weight loss reduces abdominal fat and prevents further weight gain.
Richard A Ferguson, Derek Ball, Peter Krustrup, Per Aagaard, Michael Kjær†, Anthony J Sargeant, Ylva Hellsten and Jens Bangsbo. Muscle oxygen uptake and energy turnover during dynamic exercise at different contraction frequencies in humans. The Journal of Physiology, 2005, vol. 536, no. 1, pages 261-271. Published by and copyright Wiley-Blackwell Publishing. The definitive version of this article is available from http://www.blackwell-synergy.com/ 1. It has been established that pulmonary oxygen uptake is greater during cycle exercise in humans at high compared to low contraction frequencies. However, it is unclear whether this is due to more work being performed at the high frequencies and whether the energy turnover of the working muscles is higher. The present study tested the hypothesis that human skeletal muscle oxygen uptake and energy turnover are elevated during exercise at high compared to low contraction frequency when the total power output is the same. 2. Seven subjects performed single-leg dynamic knee-extensor exercise for 10 min at contraction frequencies of 60 and 100 r.p.m. where the total power output (comprising the sum of external and internal power output) was matched between frequencies (54 ± 5 vs. 56 ± 5 W; mean ± s.e.m.). Muscle oxygen uptake was determined from measurements of thigh blood flow and femoral arterial–venous differences for oxygen content (a–v O2 diff). Anaerobic energy turnover was estimated from measurements of lactate release and muscle lactate accumulation as well as muscle ATP and phosphocreatine (PCr) utilisation based on analysis of muscle biopsies obtained before and after each exercise bout. 3. Whilst a–v O2 diff was the same between contraction frequencies during exercise, thigh blood flow was higher (P < 0.05) at 100 compared to 60 r.p.m. Thus, muscle V̇O2 was higher (P < 0.05) during exercise at 100 r.p.m. Muscle V̇O2 increased (P < 0.05) by 0.06 ± 0.03 (12 %) and 0.09 ± 0.03 l min−1 (14 %) from the third minute to the end of exercise at 60 and 100 r.p.m., respectively, but there was no difference between the two frequencies. 4. Muscle PCr decreased by 8.1 ± 1.7 and 9.1 ± 2.0 mmol (kg wet wt)−1, and muscle lactate increased to 6.8 ± 2.1 and 9.8 ± 2.5 mmol (kg wet wt)−1 during exercise at 60 and 100 r.p.m., respectively. The total release of lactate during exercise was 48.7 ± 8.8 and 64.3 ± 10.6 mmol at 60 and 100 r.p.m. (not significant, NS). The total anaerobic ATP production was 47 ± 8 and 61 ± 12 mmol kg−1, respectively (NS). 5. Muscle temperature increased (P < 0.05) from 35.8 ± 0.3 to 38.2 ± 0.2 °C at 60 r.p.m. and from 35.9 ± 0.3 to 38.4 ± 0.3 °C at 100 r.p.m. Between 1 and 7 min muscle temperature was higher (P < 0.05) at 100 compared to 60 r.p.m. 6. The estimated mean rate of energy turnover during exercise was higher (P < 0.05) at 100 compared to 60 r.p.m. (238 ± 16 vs. 194 ± 11 J s−1). Thus, mechanical efficiency was lower (P < 0.05) at 100 r.p.m. (24 ± 2 %) compared to 60 r.p.m. (28 ± 3 %). Correspondingly, efficiency expressed as work per mol ATP was lower (P < 0.05) at 100 than at 60 r.p.m. (22.5 ± 2.1 vs. 26.5 ± 2.5 J (mmol ATP)−1). 7. The present study showed that muscle oxygen uptake and energy turnover are elevated during dynamic contractions at a frequency of 100 compared with 60 r.p.m. It was also observed that muscle oxygen uptake increased as exercise progressed in a manner that was not solely related to the increase in muscle temperature and lactate accumulation.
One-leg exercise of 5 weeks duration in 10 healthy middleaged women resulted in a significant increment of muscle force in the exercising leg and in a less, but at some angular velocities also significant, increase in the nonexercising leg. The thickness of subcutaneous tissue measured by ultrasound and skinfold caliper decreased, while muscle thickness increased in the exercising leg only. The increased thickness of muscle tissue was associated with an increase in the relative number and relative fiber area of type II fibers in the exercising leg. The mean fiber area of type IIB fibers increased significantly as well as the activity of lactate dehydrogenase and myokinase. The decrease of thickness of subcutaneous adipose tissue was not associated with a significant decrease in fat cell size and was probably due to geometrical factors secondary to hypertrophy of the underlying muscle. It is concluded that the relationship between lean and fat components of the human thigh is significantly influenced by changes in the activity of the thigh skeletal muscles, but a local dynamic strength training program can hardly be used for local emptying of the fat depot over the exercising muscles.
Tissue monoacylglycerols (MG), diacylglycerols (DG), free fatty acids (FFA), and cyclic AMP (cAMP) and release of FFA and glycerol have been studied in vitro in subcutaneous adipose tissue of 6 obese and 7 normal-weight subjects. The tissue was incubated without or with 6 X 10(-5) mol/l of isoprenaline (ISNA). The DG level and the fat cell volume were strongly interrelated (r=+0.95, p less than 0.001). The concentration of DG was increased (p less than 0.05) in obesity. The changes in DG and MG were significantly interrelated (r=+0.65, p less than 0.05) during basal incubation. ISNA increased the DG concentration in a way that was correlated (r=+0.81, p less than 0.001) with the ISNA-induced glycerol release. This indicates that 1) the basal metabolic activities of MG and DG lipase are similar and 2) DG lipase is an important rate limiting factor in lipolysis. Without ISNA, tissue FFA and the release of FFA and glycerol were significantly increased in the obese patients. As a mean, MG and DG did not accumulate in the basal state in the two patient groups. The findings indicate that basal lipolysis was increased in obesity. This was probably due to increased basal metabolic activity of triacylglycerol lipase, since the basal cAMP levels were similar in the two patient groups. In the presence of ISNA, the production of FFA and the glycerol release were similar in both patient groups, as was the increase in tissue DG. Also the ISNA-induced maximal level of cAMP was similar in the two groups. With ISNA, a small increment of MG was observed in adipose tissue of the normal-weight subjects. Taking all metabolites into account, the rate of lipolysis as well as the activation of triacylglycerol lipase via cAMP in the presence of ISNA appeared to be unaltered in obesity. Separate experiments with 1-14C-glycerol provided further evidence for the existence of a MG pathway for the esterification of FFA.
Spatial solute concentration profiles resulting from in vivo microdialysis were measured in rat caudate-putamen by quantitative autoradiography. Radiolabeled sucrose was included in the dialysate, and the tissue concentration profile measured after infusions of 14 min and 61.5 min in an acute preparation. In addition, the changes in sucrose extraction fraction over time were followed in vivo and in a simple in vitro system consisting of 0.5% agarose. These experimental results were then compared with mathematical simulations of microdialysis in vitro and in vivo. Simulations of in vitro microdialysis agreed well with experimental results. In vivo, the autoradiograms of the tissue concentration profiles showed clear evidence of substantial differences between 14 and 61.5 min, even though the change in extraction fraction was relatively small over that period. Comparison with simulated results showed that the model substantially underpredicted the observed extraction fraction and overall amount of sucrose in the tissue. A sensitivity analysis of the various model parameters suggested a tissue extracellular volume fraction of approximately 40% following probe implantation. We conclude that the injury from probe insertion initially causes disruption of the blood-brain barrier in the vicinity of the probe, and this disruption leads to an influx of water and plasma constituents, causing a vasogenic edema.
In microdialysis experiments, 'recovery' estimations are required to calculate extracellular concentrations of the compounds determined. Generally, relative recovery (RR) is determined in vitro as: RR = cd/cs, with (cd) being the concentration of a compound in a dialysate fraction and (cs) its known concentration within a sample solution. To determine recoveryin vivo, relative loss (RL) was defined RL = (cp-cd)/cp with (cp-cd) being the loss of a compound from the perfusate and (cp) its perfusate concentration. RL was determined in vitro and in vivo by adding an 'internal reference compound' to the perfusate. Here, 14C-labelled lactate was used as the compound of interest. Comparing RL and RR in vitro, we found both to be similar. In vivo, however, RL was 34% of RL(in) vitro (CSF) and 46% of RL(in) vitro in agar-containing CSF. During ischaemia, RL of lactate even decreased to only 35% of the pre-ischaemic control level. We conclude that RL and RR represent inverse measurements of 'recovery.' Whereas RR can only be determined in vitro, RL can be determined in vivo. We found recoveryin vivo to be different from recoveryin vitro. Moreover, recoveryin vivo decreased during ischaemia. By means of the measured recoveryin vivo extracellular lactate concentrations prior and during ischaemia were calculated. The results, therefore, validate the 'internal reference technique' as a practical method for estimating recoveryin vivo and for controlling dialysis efficacy in vivo even continuously.
The adrenergic regulation of lipolysis was investigated in situ at rest and during standardized bicycle exercise in nonobese healthy subjects, using microdialysis of the extracellular space in subcutaneous adipose tissue. The glycerol concentration was about two times greater in adipose tissue than in venous blood. At rest, the glycerol concentration in adipose tissue was rapidly increased by 100% (P less than 0.01) after the addition of phentolamine to the ingoing perfusate, whereas addition of propranolol did not alter the adipose tissue glycerol level. Glycerol in adipose tissue and plasma increased during exercise and decreased in the postexercise period. Propranolol in the perfusate almost completely inhibited the increase in the tissue dialysate glycerol during the exercise-postexercise period. Phentolamine, however, was completely ineffective in this respect. During exercise, the lipolytic activity was significantly more marked in abdominal than in gluteal adipose tissue; this was much more apparent in women than in men. Thus, in vivo lipolysis in subcutaneous adipose tissue is regulated by different adrenergic mechanisms at rest and during exercise. Alpha-adrenergic inhibitory effects modulate lipolysis at rest, whereas beta-adrenergic stimulatory effects modulate lipolysis during exercise. In addition, regional differences in lipolysis are present in vivo during exercise, which seem governed by factors relating to sex.
In an attempt to approach a system of isolated exercising muscle in humans, a model has been developed that enables the study of muscle activity and metabolism over the quadriceps femoris (QF) muscles while the rest of the body remains relaxed. The simplest version includes the subject sitting on a table with a rod connecting the ankle and the pedal arm of a bicycle ergometer placed behind the subject. Exercise is performed by knee extension from a knee angle of 90 to approximately 170 degrees while flywheel momentum repositions the relaxed leg during flexion. Experiments where electromyographic recordings have been taken from biceps femoris, gastrocnemius, tibialis anterior, and other muscles in addition to QF indicate that only the QF is active and that there is an equal activation of the lateral, medial, and rectus femoris heads relative to maximum. Furthermore, virtually identical pulmonary O2 uptake (Vo2) during and without application of a pressure cuff below the knee emphasizes the inactivity of the lower leg muscles. The advantages of the model are that all external work can be localized to a single muscle group suitable for taking biopsies and that the blood flow in and sampling from the femoral vein are representative of the active muscles. Thus all measurements can be closely related to changes in the working muscle. Using this model we find that a linear relationship exists between external work and pulmonary Vo2 over the submaximal range and the maximal Vo2 per kilogram of muscle may be as much as twice as high as previously estimated.
This study was designed to determine if the skinfold measurements on an exercised arm would decrease as a result of regular weight training with that arm. Thirty-two subjects completed three sets of 7-RM curls and three sets of 7-RM triceps extensions on either a daily or an alternate day schedule for a period of 6 weeks. The nonexercised arm was measured to establish the specificity of the spot reduction on the exercised arm. The results indicate that hard exercise in a specific area of the arm will result in a reduction of the subcutaneous adipose tissue in that area.
Circulatory metabolic and cardiovascular responses to 1-h-long infusions of norepinephrine (NE) (approx. 0.2 and 0.4 nmol/kg body weight per min) were measured on two separate occasions in six subjects. The infusions increased circulating NE concentrations 6- and 13-fold, respectively. Blood flow to adipose tissue, measured with the 133Xe clearance technique, increased from a basal value of about 3 ml/100 g per min, to about twice this value at 60 min with both doses of NE. In contrast muscle blood flow was unaffected. The higher dose of NE produced significant increments at 60 min in whole body oxygen consumption (approx. 9%), and circulating concentrations of glucose (approx. 18%), non-esterified fatty acids (approx. 200%) and glycerol (approx. 32%) which were greater than those observed with the low-dose infusion. Changes in blood pressure, pulse and CO2 exchange were observed within 5-10 min after the start of the infusion, whilst changes in adipose tissue blood flow were observed after 15-30 min. It is concluded that in humans (i) a dose of NE as low as 0.2 nmol/kg per min is sufficient to evoke both circulatory and metabolic responses; (ii) the pattern in the adipose tissue blood flow response to NE may help explain some of the conflicting reports about the haemodynamic effects of this hormone in adipose tissue; and (iii) blood flow and vascular resistance in different tissues may be affected in different ways by norepinephrine.
1. To investigate the link between post-prandial thermogenesis and sympathetic nervous activation we have studied the effects of a single large meal on regional sympathetic nervous activity in healthy, lean subjects.
2. In nine male subjects, noradrenaline spillover was measured from the heart, kidney and liver using isotope dilution, both while fasting and after consumption of a high-energy liquid meal of composition 53% carbohydrate, 32% fat and 15% protein (energy value 2.64–3.51 MJ). Regional oxygen consumption, whole-body oxygen consumption and, in a subset of subjects, muscle sympathetic nerve firing (microneurography) were also measured.
3. Both whole-body oxygen consumption (P < 0.03) and total body spillover of noradrenaline (P < 0.01) rose after the meal, with peak increases of 24% and 56% respectively. Spillover of noradrenaline from the heart was unchanged, that from the hepatosplanchnic circulation increased marginally (0.377 nmol/min to 0.480 nmol/min, P = 0.09), while renal noradrenaline spillover more than doubled (0.440 nmol/min to 0.937 nmol/min, P < 0.05). Skeletal muscle sympathetic nerve activity (peroneal nerve) increased from 7.7 bursts/min at rest to peak at 17.9 bursts/min 60 min after the meal in the three subjects in whom stable recordings were obtained.
4. The meal increased oxygen consumption in the kidneys and liver significantly, from 11.5 ± 1.6 ml/min to 14.5 ± 1.1 ml/min and from 46 ± 7 ml/min to 57 ± 6 ml/min respectively (P < 0.05), but not in the heart.
5. Consumption of a large meal produces a substantial and relatively selective increase in sympathetic outflow to the kidneys and skeletal muscle. While resting regional oxygen consumptions and noradrenaline spillovers were related, the changes that occurred in each were unrelated, so that no direct relationship could be demonstrated between post-prandial thermogenesis and sympathetic activity.
A new method to calculate the tissue/blood partition coefficient (Λ) for xenon in studies on the subcutaneous adipose tissue blood flow was compared with a previously reported method based on local skinfold thickness (ΛLSt). The former method included needle biopsies from the abdominal and femoral subcutaneous adipose tissue, and the mean fat cell diameter was measured (ΛECT)- The extracellular tissue fraction in subcutaneous tissue was then estimated from a diagram. The tissue lipid content was approximated to equal the relative intracellular volume and Ostwald's solubility coefficients for 133Xe, based on the distribution of xenon in lipid, albumin and 0.9% saline were applied. Estimated Λ-values based on needle biopsies from the abdominal site were: 8.6±0.1 versus 9.9±0.4 ml g-1 (meanæ) (P<0.05) and from the femoral site: 9.1±0.1 versus 9.6±0.2 in lean (n=10) and obese subjects (n=10), respectively. The corresponding Λ-values obtained from skinfold measurements were: 6.2±0.5 versus 11.0±0.4 (P<0.001) and 6.9±03 versus 11.4±0.4 (P<0.001) in lean and obese subjects, respectively.
Pooled ΛLsT-values correlated positively with estimated adipose tissue blood flow (ATBF) (r: 0.34, P<0.05, n=40) whereas no such correlation was found for ΛECT-values.
In conclusion, a new method is presented which may allow an accurate determination of, and which may lead to reliable data on, subcutaneous ATBF in both lean and obese subjects. Comparative studies indicate that the widely used Λ-value of 10.0 in subcutaneous adipose tissue may be used as a rough estimate for subcutaneous blood flow studies in these patient groups.
The direct influence of the sympathetic nervous system on white adipose tissue was studied by performing a unilateral surgical denervation of the retroperitoneal fat pad in rats, the contralateral pad being used as a control. One week after surgery, the weight of the denervated pad was significantly higher than that of the intact pad. In vivo, glucose utilization was not altered by denervation. The expression of GLUT4 as well as the expression and activity of fatty acid synthase, lipoprotein lipase, and hormone-sensitive triglyceride lipase were similar in the two pads. Lipolysis in response to norepinephrine, determined in vitro, was not modified by denervation although the ratio between alpha 2- and beta-adrenergic receptors was changed. Denervation induced an increase in DNA content without change in the number of mature adipocytes. The expression of A2COL6/pOb24, a marker of the early step of adipocyte differentiation, was significantly enhanced in the denervated pad, suggesting an increased number of preadipocytes. This was confirmed by an increased cell number observed in the denervated fat pad 1 month after surgery. In conclusion, surgical denervation of the white fat pad does not alter the glucose and lipid metabolisms. By contrast, it accelerated adipocyte differentiation and led to the recruitment of new precursors.
Trained humans (Tr) have a higher fat oxidation during submaximal physical work than sedentary humans (Sed). To investigate whether this reflects a higher adipose tissue lipolytic sensitivity to catecholamines, we infused epinephrine (0.3 nmol.kg-1.min-1) for 65 min in six athletes and six sedentary young men. Glycerol was measured in arterial blood, and intercellular glycerol concentrations in abdominal subcutaneous adipose tissue were measured by microdialysis. Adipose tissue blood flow was measured by 133Xe-washout technique. From these measurements adipose tissue lipolysis was calculated. During epinephrine infusion intercellular glycerol concentrations were lower, but adipose tissue blood flow was higher in trained compared with sedentary subjects (P < 0.05). Glycerol output from subcutaneous tissue (Tr: 604 +/- 322 nmol.100 g-1.min-1; Sed: 689 +/- 203; mean +/- SD) as well as arterial glycerol concentrations (Tr: 129 +/- 36 microM; Sed: 119 +/- 56) did not differ between groups. It is concluded that in intact subcutaneous adipose tissue epinephrine-stimulated blood flow is enhanced, whereas lipolytic sensitivity to epinephrine is the same in trained compared with untrained subjects.
To investigate the feasibility of the microdialysis ethanol perfusion technique for monitoring nutritive blood flow in subcutaneous adipose tissue.
Microdialysis probes were inserted percutaneously into the subcutaneous adipose tissue in 15 non-obese women, and were perfused with 50 mmol/l of ethanol. The experiments were carried out during basal conditions and in conjunction with local vasodilation induced by external heating. The ethanol exchange ratio (ethanol concentration in the outgoing tissue dialysate vs ethanol concentration in the ingoing perfusate) was determined. A comparison was made with the 133Xe clearance technique to assess the adipose tissue blood flow.
At rest, the ethanol exchange ratio in the individual subjects was inversely correlated to the adipose tissue blood flow, as measured with 133Xe wash-out (r = -0.78-0.82, p < 0.05-0.01). When the subcutaneous temperature was increased in a stepwise fashion by external heating, adipose tissue blood flow, as determined with 133Xe clearance, was increased by about 50% and 100%, respectively, above resting values (F = 26.7, p < 0.0001). At the same time, the ethanol exchange ratio was progressively and significantly (F = 24.6, p < 0.0001) reduced. In the individual subjects there was a close negative correlation (r = -0.90-0.94) between the ethanol exchange ratios and the corresponding adipose tissue blood flow values, as measured by 133Xe clearance, in response to local vasodilation.
The microdialysis ethanol perfusion technique provides a valid indicator of small changes within the physiological range in adipose tissue blood flow.
We used the perfused rat hindquarter to evaluate whether the microdialysis ethanol technique can be used to qualitatively estimate nutritive skeletal muscle blood flow. Four microdialysis probes were inserted in different hindlimb muscles in each of 16 rats. Hindquarters were perfused at blood flow rates ranging from 0 to 21 ml. 100 g-1. min-1. The microdialysis probes were perfused at 2 microliter/min with perfusate containing ethanol, [14C]ethanol, and 3H2O. Within and between experiments outflow-to-inflow ratios (o/i) generally varied inversely with blood flow. When a low flow or no flow was maintained in hindquarters, o/i ratios first increased with time (for at least 60 min) and then leveled off. The long time constant impaired detection of rapid oscillations in blood flow, especially at low blood flow rates. Contractions per se apparently decreased o/i ratios independent of blood flow. Ethanol and [14C]ethanol o/i ratios did not differ. 3H2O o/i paralleled ethanol and [14C]ethanol o/i ratios but it was significantly lower. In conclusion, differences in skeletal muscle blood flow can be detected by the microdialysis technique. However, the slow changes in o/i, in particular at low blood flow rates, limit the usefulness of the technique for measuring dynamic changes in blood flow; caution must also be exerted during muscle contractions. 3H2O and [14C]ethanol are good alternatives to ethanol in the determination of blood flow by microdialysis.
1. The effect of intraneural electrical stimulation of the lateral femoral cutaneous nerve on lipolysis in the innervation territory of the stimulated nerve fascicle was studied in seven healthy women. Lipolysis was evaluated by microdialytic measurement of the interstitial glycerol concentration in subcutaneous adipose tissue. 2. Ten minutes of unilateral intraneural stimulation elicited a 22 +/- 8 % (mean +/- s.e.m.) increase in glycerol levels in the stimulated region (P < 0.05), whereas no change was registered in the corresponding area of the contralateral unstimulated leg. 3. Significantly higher glycerol levels in the stimulated vs. contralateral unstimulated region (47 +/- 13 %, P < 0.05) were already observed at baseline (30 min resting period preceding the 10 min stimulation), in all probability as a consequence of the nerve searching procedure and trial stimulations. After the 10 min stimulation, the overall glycerol increase was 72 +/- 17 % compared with the contralateral leg, illustrating the degree of lipolysis induced by the whole experimental procedure. 4. The sympathetic discharge in the lateral femoral nerve (6 recordings) showed typical characteristics of skin sympathetic activity, and the firing pattern was strikingly similar to simultaneously recorded sympathetic discharge in cutaneous nerve fascicles innervating regions without prominent subcutaneous fat stores (2 double nerve recordings). Thus, no component of cutaneous sympathetic outflow specific for the nerve innervating prominent subcutaneous fat stores could be identified. 5. Our findings suggest that sympathetic nerve fibres travelling in cutaneous nerve fascicles exert a regulatory influence on subcutaneous fat tissue in humans. The combination of intraneural recording/stimulation and subcutaneous microdialysis provides a model for evaluating neural control of human fat metabolism.
Endurance training increases fatty acid oxidation (FAO) and skeletal muscle oxidative capacity. However, the source of the additional fat and the mechanisms for increasing FAO capacity in muscle are not clear. We measured whole body and regional lipolytic activity and whole body and plasma FAO in six lean women during 90 min of bicycling exercise (50% pretraining peak O(2) consumption) before and after 12 wk of endurance training. We also assessed skeletal muscle content of peroxisome proliferator-activated receptor-alpha (PPARalpha) and its target proteins that regulate FAO [medium-chain and very long chain acyl-CoA dehydrogenase (MCAD and VLCAD)]. Despite a 25% increase in whole body FAO during exercise after training (P < 0.05), training did not alter regional adipose tissue lipolysis (abdominal: 0.56 +/- 0.26 and 0.57 +/- 0.10 micromol x 100 g(-1) x min(-1); femoral: 0.13 +/- 0.07 and 0.09 +/- 0.02 micromol x 100 g(-1) x min(-1)), whole body palmitate rate of appearance in plasma (168 +/- 18 and 150 +/- 25 micromol/min), and plasma FAO (554 +/- 61 and 601 +/- 45 micromol/min). However, training doubled the levels of muscle PPARalpha, MCAD, and VLCAD. We conclude that training increases the use of nonplasma fatty acids and may enhance skeletal muscle oxidative capacity by PPARalpha regulation of gene expression.
1. The relative roles of sympathetic nerve activity and circulating catecholamines for adipose tissue lipolysis during exercise are not known. 2. Seven paraplegic spinal cord injured (SCI, injury level T3-T5) and seven healthy control subjects were studied by microdialysis and (133)xenon washout in clavicular (Cl) and in umbilical (Um) (sympathetically decentralized in SCI) subcutaneous adipose tissue during 1 h of arm cycling exercise at approximately 60 % of the peak rate of oxygen uptake. 3. During exercise, adipose tissue blood flow (ATBF) and interstitial glycerol, lactate and noradrenaline concentrations increased significantly in both groups. Plasma catecholamine levels increased significantly less with exercise in SCI than in healthy subjects. The exercise-induced increase in interstitial glycerol concentration in subcutaneous adipose tissue was significantly lower in SCI compared with healthy subjects (SCI: 25 +/- 12 % (Cl), 36 +/- 20 % (Um); healthy: 60 +/- 17 % (Cl), 147 +/- 45 % (Um)) and the increase in ATBF was significantly lower (Cl) or similar (Um) in SCI compared with healthy subjects (SCI: 1.2 +/- 0.3 ml (100 g)(-1) min(-1) (Cl), 1.0 +/- 0.3 ml (100 g)(-1) min(-1) (Um); healthy: 2.8 +/- 0.7 ml (100 g)(-1) min(-1) (Cl), 0.6 +/- 0.3 ml (100 g)(-1) min(-1) (Um)). Accordingly, in both adipose tissues lipolysis increased less in SCI compared with healthy subjects, indicating that circulating catecholamines are important for the exercise-induced increase in subcutaneous adipose tissue lipolysis. In SCI subjects, the exercise-induced increase in subcutaneous adipose tissue lipolysis was not lower in decentralized than in sympathetically innervated adipose tissue. During exercise the interstitial noradrenaline and adrenaline concentrations were lower in SCI compared with healthy subjects (P < 0.05) and always lower than arterial plasma catecholamine concentrations (P < 0.05). 4. It is concluded that circulating catecholamines are important for the exercise-induced increase in subcutaneous adipose tissue lipolysis while sympathetic nerve activity is not.
Interleukin-6 (IL-6) was infused intravenously for 2.5 h in seven healthy human volunteers at a dose giving rise to a circulating IL-6 concentration of approximately 35 ng l(-1). The metabolic effects of this infusion were studied in subcutaneous adipose tissue on the anterior abdominal wall and in the splanchnic tissues by the Fick principle after catheterizations of an artery, a subcutaneous vein draining adipose tissue, and a hepatic vein, and measurements of regional adipose tissue and splanchnic blood flows. In control studies without IL-6 infusion subcutaneous adipose tissue metabolism was studied by the same technique in eight healthy subjects. The net release of glycerol and fatty acids from the subcutaneous abdominal adipose tissue remained constant in the control experiment. IL-6 infusion gave rise to increase in net glycerol release in subcutaneous adipose tissue while the net release of fatty acids did not change significantly. In the splanchnic region IL-6 elicited a pronounced vasodilatation, and the uptake of fatty acids and the gluconeogenic precursors glycerol and lactate increased significantly. The splanchnic net output of glucose and triacylglycerol did not change during the IL-6 infusion. It is concluded that IL-6 elicits lipolytic effects in human adipose tissue in vivo, and that IL-6 also has effects on the splanchnic lipid and carbohydrate metabolism.
The concentration of plasma interleukin-6 (IL-6) increases during physical exercise, but until recently the cellular origin of this increase has been unknown. Recent work has identified that skeletal muscle is a major source of this increase and the release of IL-6 from muscle can mediate metabolic processes. IL-6 is, therefore, the first identified "myokine" released from muscle that can now be termed an endocrine organ.
Obesity is an established risk factor for numerous chronic diseases, and successful treatment will have an important impact on medical resources utilization, health care costs, and patient quality of life. With over 60% of our population being overweight, physicians face a major challenge in assisting patients in the process of weight loss and weight-loss maintenance. Low-calorie diets can lower total body weight by an average of 8% in the short term. These diets are well-tolerated and characterize successful strategies in maintaining significant weight loss over a 5-year period. Very-low-calorie diets produce a more rapid weight loss but should only be used for fewer than 16 weeks because of clinical adverse effects. Diets that are severely restricted in carbohydrates (3%-10% of total energy intake) and do not emphasize a reduction of energy intake may be effective in reducing weight in the short term, but there is no evidence that they are sustainable or innocuous in the long term because their high saturated-fat content may be atherogenic. Fat restriction in a weight-loss regimen is beneficial, but the optimal percentage has yet to be determined. Longitudinal trials are needed to resolve these issues. In this article I discuss the evidence for and pitfalls of various types of weight-loss diets and identify issues that physicians need to address in weight loss and weight-loss maintenance.
analysis: effect of exercise, with or without dieting, on the body composition of overweight subjects
- J S Garrow
- Meta