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Fatmax: A new concept to optimize fat oxidation during exercise?

DOI:10.1080/17461390100071507
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Asker Jeukendrup at Loughborough University
Asker Jeukendrup
Juul Achten
Juul Achten
Juul Achten
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It has been recognized that facilitation of fat metabolism is important for both performance and the health-related aspects of exercise. Although several studies have described the relationship between exercise intensity and fat oxidation, few studies have studied this relationship over a wide range of intensities. In absolute terms, carbohydrate oxidation will increase proportionally with exercise intensity, whereas the rate of fat oxidation will initially increase but will decrease again at high exercise intensities. Here we have defined the exercise intensity at which maximal fat oxidation is observed as Fatmax. This exercise intensity may have importance for weight loss programs, health-related exercise programs, and endurance training. Future research should focus on developing an exercise test with which Fatmax can be accurately determined. Further research should investigate the efficacy of training at Fatmax in a variety of conditions. Key Points: • It has been recognized that facilitation of fat metabolism is important for both performance and the health-related aspects of exercise. • In absolute terms, carbohydrate oxidation will increase proportionally with exercise intensity, whereas the rate of fat oxidation will initially increase but will decrease again at high exercise intensities. • Here we have defined the exercise intensity at which maximal fat oxidation is observed as Fatmax. • Fatmax may have importance for weight loss programs, health-related exercise programs, and endurance training. Introduction Much of the emphasis of exercise programs for obese patients, and endurance training for athletes, is on cardiovascular and respiratory benefits, and increasing the oxidative capacity of skeletal muscle (3, 11). Fat metabolism, however, is an area that has received less attention, even though its importance has been recognized for both performance and the health-related aspects of exercise (14–17, 25).
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European Journal of Sport Science, vol. 1, issue 5
©2001 by Human Kinetics Publishers and the European College of Sport Science
Fatmax: A New Concept
to Optimize Fat Oxidation During Exercise?
Asker E. Jeukendrup and Juul Achten
It has been recognized that facilitation of fat metabolism is important for both
performance and the health-related aspects of exercise. Although several studies have
described the relationship between exercise intensity and fat oxidation, few studies have
studied this relationship over a wide range of intensities. In absolute terms, carbohydrate
oxidation will increase proportionally with exercise intensity, whereas the rate of fat
oxidation will initially increase but will decrease again at high exercise intensities. Here
we have defined the exercise intensity at which maximal fat oxidation is observed as
Fatmax. This exercise intensity may have importance for weight loss programs, health-
related exercise programs, and endurance training. Future research should focus on
developing an exercise test with which Fatmax can be accurately determined. Further
research should investigate the efficacy of training at Fatmax in a variety of conditions.
Key Words: exercise intensity, fuel oxidation, fat metabolism
Key Points:
• It has been recognized that facilitation of fat metabolism is important for both
performance and the health-related aspects of exercise.
• In absolute terms, carbohydrate oxidation will increase proportionally with exercise
intensity, whereas the rate of fat oxidation will initially increase but will decrease again at
high exercise intensities.
• Here we have defined the exercise intensity at which maximal fat oxidation is observed
as Fatmax.
• Fatmax may have importance for weight loss programs, health-related exercise
programs, and endurance training.
Introduction
Much of the emphasis of exercise programs for obese patients, and endurance training for
athletes, is on cardiovascular and respiratory benefits, and increasing the oxidative capacity of
skeletal muscle (3, 11). Fat metabolism, however, is an area that has received less attention, even
though its importance has been recognized for both performance and the health-related aspects of
exercise (14–17, 25).
Endurance performance is largely determined by the ability of the athlete to mobilize and oxidize
fat to spare reserves of carbohydrates, and this is most likely susceptible to specific training (13).
In weight control programs, exercise is used alone or in conjunction with a dietary restriction.
When exercise is the only intervention, the main goal is to reduce body fat (9, 22, 30). When
combined with a diet program, it is mainly used to counteract the decrease in fat oxidation often
2 Jeukendrup and Achten
seen after weight loss (2, 7, 23). In a variety of clinical conditions, exercise may be beneficial
through changes in fat metabolism. For example, an increased capacity to oxidize fat as a fuel in
diabetic patients will make them less dependent on glucose as a source of energy (29). Although
it is generally agreed that exercise programs will increase the capacity to oxidize fat, there is
controversy as to what exercise intensity or training program should be employed in order to
achieve the aims of all three groups, and guidelines are generally inconsistent.
The purpose of this short review is not to describe new factual information but to provide new
ideas, introduce a new concept, and expand the boundaries of our thinking about exercise
training in relation to fat metabolism.
Fat Oxidation During Exercise
Effect of Exercise Intensity on Fat Oxidation
Already in 1939, Christensen and Hansen (4) observed that changes in the exercise intensity
induced changes in substrate utilization. With increasing exercise intensity, the relative
contribution of carbohydrate as a fuel will increase; concomitantly, the relative contribution of
fat oxidation decreases. However, in absolute terms, carbohydrate oxidation will increase
proportionally with the exercise intensity, whereas the rate of fat oxidation will initially increase
but will decrease again at high exercise intensities (21). At intensities where the rate of
glycolysis has increased considerably (at exercise intensities above lactate threshold), relatively
less fatty acids will be used as a fuel, and although the energy expenditure is increasing, absolute
rates of fat oxidation will actually decrease. In Figure 1, fat oxidation is depicted versus the
exercise intensity expressed as VO2. The data are based on the theoretical calculation based on
stoichiometric equations (8), where the respiratory exchange ratio (RER) increases linearly from
0.86 (an average resting RER) to 1.00 as VO2 increases linearly from 1.2 to 4.0 L/min. The
exercise intensity at which fat oxidation is optimal will thus be somewhere between the low and
the high intensity exercise. Here, we would like to introduce the term Fatmax to describe the
exercise intensity at which fat oxidation is maximal. To our knowledge, at present, no studies
have attempted to identify this exercise intensity systematically and accurately.
Figure 1 — Theoretical curve indicating fat oxidation as a function of exercise intensity (VO2). The
exercise intensity at which the highest rate of fat oxidation is observed is referred to as Fatmax.
Fatmax: A New Concept? 3
Mechanisms Behind Fatmax
Most likely, Fatmax will be just below the intensity where the rate of glycolysis commences to
increase markedly. Recently, we and others have shown that increasing the rate of glycolysis by
feeding subjects high carbohydrate pre-exercise feedings (6) or by increasing the exercise
intensity from 40 to 70% VO2max (24) decreases the oxidation of long chain fatty acids but not of
medium chain fatty acids. This suggested that increasing rates of glycolysis inhibit fat oxidation
by inhibiting the CPT-1 and carnitine-mediated transport of fatty acids into mitochondria. In
addition, several studies reported a decreased rate of appearance of fatty acids into the circulation
during intense exercise, suggesting that the mobilization of fatty acids is decreased. This could
be linked to reduced rates of lipolysis or reduced blood flow to the adipose tissue (for review, see
14–17). Because fat oxidation is directly dependent on the rate of glycolysis, Fatmax might
coincide with the onset of blood lactate accumulation. This hypothesis has not been tested.
Potential Applications of Fatmax
Exercise training programs at an intensity that elicits maximal rates of fat oxidation (i.e.,
Fatmax) may be useful in a variety of conditions and for a variety of populations. For example, it
could have implications for exercise programs to treat and prevent cardiovascular diseases,
obesity, and non-insulin-dependent Diabetes Mellitus (NIDDM). It could also be used in general
weight reduction programs and for athletes as a means to increase one’s capacity to oxidize fat.
Training Programs for Athletes. One of the main adaptations to endurance training is a shift
from carbohydrate towards fat metabolism (12, 13, 28). The ability to oxidize fat as a fuel is also
highly correlated with exercise performance (12, 13). Training of endurance athletes therefore
often includes training sessions that specifically aim to improve fat metabolism. Training at an
exercise intensity at which metabolic pathways involved in fat metabolism are maximally
activated could, at least theoretically, result in optimal adaptations in these pathways. This
however has not yet been investigated.
Exercise Programs to Lose Weight or Body Fat. A recent meta-analytical review reported that
a decrease in bodyweight of 0.2 kg/week can be achieved by following an exercise program (19).
The studies showed great variety in the exercise prescription for the obese population. The same
review also suggested that exercise is critical in weight maintenance. A smaller percentage of the
weight loss induced by a restricted diet will be regained when an exercise program is followed
during and after the diet period. However, the best exercise type, intensity, and duration are still
unclear. The latest recommendation of an expert panel from the Centers for Disease Control and
the American College of Sports Medicine consist of 30 min or more of moderate-intensity
physical activity on most days of the week (1). The objective of this recommendation is to
encourage more participation in physical activity. For obese individuals, the frequency, intensity,
and duration of exercise are more focussed on increasing energy expenditure than on increasing
fat oxidation. Finding the optimal intensity for fat oxidation might increase weight loss and
support weight maintenance.
Exercise Programs to Treat or Prevent Welfare Diseases. There is considerable interest in
finding treatments and preventive measures to avoid overweight, obesity, and associated diseases
like NIDDM, arteriosclerosis, and hypertension (26). Exercise has been shown to significantly
decrease the risk of developing such diseases (18, 27). However, there is controversy as to what
4 Jeukendrup and Achten
type of exercise and what exercise intensity would be most effective in reducing this risk. Since
many of these disease states are linked to high levels of circulating triglycerides and disturbance
in fat metabolism (5, 10, 20, 29), it is tempting to think that exercise intensities at which a
maximal amount of fat is oxidized (Fatmax) would be a preferred intensity. Therefore,
determination of Fatmax could also be a useful tool to design exercise programs in order to
obtain optimal health benefits.
Conclusions and Directions for Future Research
The concept of Fatmax seems promising and may be an efficient exercise intensity for weight
loss programs, health-related exercise programs, and endurance training. Future research should
focus on developing an exercise test with which Fatmax can be accurately determined, and such
a test needs to be validated and tested for reliability. Further research should investigate the
efficacy of training at Fatmax under a variety of conditions, and methods should be developed to
monitor exercise intensity during training.
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Fatmax: A New Concept? 5
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About the Authors
A.E. Jeukendrup and J. Achten are with the Human Performance Laboratory in the School of
Sport and Exercise Sciences at the University of Birmingham, Edgbaston, Birmingham, UK.
Asker Jeukendrup <A.E.Jeukendrup@bham.ac.uk> is a lecturer at the School of Sport and
Exercise Sciences at the University of Birmingham (UK) and Academic Director of the Human
Performance Laboratory. He completed his Ph.D. in 1997 at Maastricht University in the
Netherlands and has published over 50 peer-reviewed journal articles and book chapters.
Following an M.Sc. in Biological Health Sciences at Maastricht University in the Netherlands,
Juul Achten <J.Achten@bham.ac.uk> started her Ph.D. at the University of Birmingham in the
UK in 1999. Her research in the School of Sport and Exercise Sciences focuses on fat
metabolism and heart rate monitoring.
... During exercise, the fat oxidation rate follows a curvilinear pattern, and as the exercise workload progressively augments, fat oxidation increases to its maximal oxidation rate called FAT max , a term used to describe an intensity at which the energy contribution from lipids is at its highest [2,3]. As the workload progresses toward heavy-to-severe exercise intensities, lipid oxidation decreases and carbohydrates become the predominant energy substrate with lipids becoming negligible [4]. With the body's limited storage capacity for carbohydrates, optimizing substrates' availability is recognized as one of key factors limiting the performance during high intensity and prolonged exercise [5]. ...
... Two reviewers (PR and NZ) independently developed and conducted the search in accordance with the PRISMA statement [32]. Moreover, given that the FAT max concept was initially referred to in 2001 [4], the search included publications from 1 January 2001 to 30 March 2022. ...
... Finally, a priori determination of a clinical and physiologically practical acceptable range of the LoA was based on the concept of FAT max zone (i.e., range of exercise intensities with fat oxidation rates within 10% of fat oxidation rates at FAT max ) [4], which was estimated using a meta-analytical approach (Supplementary Material Section S1) [49]. If the LoA failed within the FAT max zone reported for the corresponding measurement unit, then AerT could be used for optimizing fat oxidation with an acceptable error. ...
Factors Determining the Agreement between Aerobic Threshold and Point of Maximal Fat Oxidation: Follow-Up on a Systematic Review and Meta-Analysis on Association
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Regular exercise at the intensity matching maximal fat oxidation (FATmax) has been proposed as a key element in both athletes and clinical populations when aiming to enhance the body's ability to oxidize fat. In order to allow a more standardized and tailored training approach, the connection between FATmax and the individual aerobic thresholds (AerT) has been examined. Although recent findings strongly suggest that a relationship exists between these two intensities, correlation alone is not sufficient to confirm that the intensities necessarily coincide and that the error between the two measures is small. Thus, this systematic review and meta-analysis aim to examine the agreement levels between the exercise intensities matching FATmax and AerT by pooling limits of agreement in a function of three parameters: (i) the average difference, (ii) the average within-study variation, and (iii) the variation in bias across studies, and to examine the influence of clinical and methodological inter-and intra-study differences on agreement levels. This study was registered with PROSPERO (CRD42021239351) and ClinicalTrials (NCT03789045). PubMed and Google Scholar were searched for studies examining FATmax and AerT connection. Overall, 12 studies with forty-five effect sizes and a total of 774 subjects fulfilled the inclusion criteria. The ROBIS tool for risk of bias assessment was used to determine the quality of included studies. In conclusion, the overall 95% limits of agreement of the differences between FATmax and AerT exercise intensities were larger than the a priori determined acceptable agreement due to the large variance caused by clinical and methodological differences among the studies. Therefore, we recommend that future studies follow a strict standardization of data collection and analysis of FATmax-and AerT-related outcomes.
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... Актуальность исследования Термин Fatmax впервые использован A. Jeukendrup [7]. Под ним подразумевается интенсивность упражнения, соответствующая максимальной скорости окисления жира (СОЖ). ...
... Под ним подразумевается интенсивность упражнения, соответствующая максимальной скорости окисления жира (СОЖ). Определение Fatmax возможно при помощи газометрического оборудования [2,7]. Термин «аэробный порог» (АэП) впервые использован в исследовании W. Kindermann (1979); под ним понимается наибольшая интенсивность нагрузки, соответствующая верхнему пределу преимущественно аэробного метаболизма. ...
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По данным литературного обзора Peric et al., 2022, интенсивность упражнения (Fatmax), на которой происходит наибольшая скорость окисления жира, у спортсменов статистически не различается и тесно взаимосвязана с аэробным порогом (АэП). В последнее время широкую популярность приобрела формула Маффетона, которая позволяет приблизительно определить ЧСС (ЧССMAF), соответствующую Fatmax (для тренированных спортсменов ЧССMAF = 180 – возраст + 5). В нашем исследовании проведено 15 ступенчатых тестов на тредбане, в которых по соответствию ЧССMAF определялась скорость бега, соответствующая предполагаемой Fatmax (υMAF). По динамике накопления лактата определялась скорость АэП (υАэП). Попарно сравнивали значения ЧССАэП и ЧССMAF, и соответствующие им значения скорости и концентрации лактата (La).
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... Lipids and carbohydrates are the dominant fuels utilized by humans during exercise with their absolute and relative contribution being influenced by sex, diet, exercise intensity and duration, time of the day, and fitness level [1]. During moderate exercise intensities, the energy contribution from lipids increases and then markedly declines to zero at heavy to severe exercise intensities; from that point on, carbohydrates become the dominant energy substrate [2,3]. Carbohydrates, due to their limited stores, can reduce performance during prolonged and/or heavy intensity activities; yet, as little as 1% of body fat can supply sufficient energy for up to 90 km of physical movement, making fat a more suitable fuel source [2]. ...
... During moderate exercise intensities, the energy contribution from lipids increases and then markedly declines to zero at heavy to severe exercise intensities; from that point on, carbohydrates become the dominant energy substrate [2,3]. Carbohydrates, due to their limited stores, can reduce performance during prolonged and/or heavy intensity activities; yet, as little as 1% of body fat can supply sufficient energy for up to 90 km of physical movement, making fat a more suitable fuel source [2]. Maximal fat oxidation point (FAT max ) is commonly used to describe an exercise intensity at which fat oxidation is at its highest, whereas exercise intensity matching negligible fat oxidation is labeled FAT min [3,4]. ...
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View
... The FATmax zone occurs in a range of 10% of the peak of fat oxidation identified in a previous test (Jeukendrup and Achten, 2001). Compared to the other zones, this one provides higher fat oxidation per minute (Jeukendrup and Achten, 2001). ...
... The FATmax zone occurs in a range of 10% of the peak of fat oxidation identified in a previous test (Jeukendrup and Achten, 2001). Compared to the other zones, this one provides higher fat oxidation per minute (Jeukendrup and Achten, 2001). In our study, this zone corresponded to 40.95 ± 14.6% V O2max, which is similar to previously published articles (Tolfrey, Jeukendrup and Batterham, 2010;Suk et al., 2015;Dandanell et al., 2017), and normative values (Maunder, Plews and Kilding, 2018). ...
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Giriş Obezite; beslenme ile alınan enerji miktarının harcanan enerji miktarından fazla olması halin-de vücudun çeşitli bölgelerinde yağ dokusunun artmasıyla karakterize bir hastalık olduğu bilinen bir gerçektir. Bireylerde kilo alımı ve aşırı yağlanmanın te-mel nedenlerinin; dengesiz beslenme, teknolojik gelişimler sebebiyle pasif yaşama neden olan çalışma alanlarının artması, kentleşme ile birlik-te ulaşımdaki gelişmelerin hareketsiz yaşamı ar-tırması, çevresel ve toplumsal değişiklikler, sağ-lıklı yaşamı destekleyici politikaların eksikliği ile birlikte yüksek oranda şeker ve yağ içeren besin öğelerinin yoğun alımı olduğu görülmektedir. Obezitenin günümüz dünyasında oldukça yaygınlaşarak küresel bir sağlık sorunu haline gelmesi sonucu; Dünya Sağlık Örgütünün (WHO) yayınladığı verilere göre dünya genelinde 2016 yılında, 18 yaş ve üstü 1,9 milyardan fazla yetişki-nin (%39) fazla kilolu ve 650 milyon bireyin obez olduğu (%13) bildirilmiştir. 1975'den 2020 yılına kadar obezitenin 3 kat arttığı ve 2016 yılında 5-19 yaş arası 340 milyon çocuk ve ergenin, 2019 yılın-da 5 yaş altındaki 38 milyon çocuğun fazla kilolu ve obez olduğu belirtilmektedir. (1) Obezite; insanların yaşam kalitesini önemli düzeyde olumsuz etkilediği gibi beraberinde bir-çok hastalığa da sebep olduğu ve obez olmayan bireylere göre kronik hastalıkların görülme sıklığı-nı da oldukça artırdığı bilinmektedir. (2) Bazı araş-tırmalarda; obez ve kilolu bireylerde kronik has-talık görülme oranının %47,8, (3) erkek olan obez bireylerde kronik hastalık bulunma oranı %33,7 iken obez olan kadın bireylerde ise %44,4 (4) ve 65 yaş üstü obez bireylerde kronik hastalık görülme oranı %44.5 olarak bildirilmiştir. (5) Bazı araştır-malarda ise; obezlerin kilo vermeleri durumunda
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... We observed that RPE increased with time, although there was no difference between the phases in the GTE and PLA trials. The increase in exercise intensity was accompanied by a decrease in fat oxidation [55]. That is, the exercise intensity in this study may have fluctuated relative to the physical condition of the participants on the day of the study and may have affected energy substrate utilization. ...
Effect of Green Tea Extract Ingestion on Fat Oxidation during Exercise in the Menstrual Cycle: A Pilot Study
Article
Full-text available
  • Sep 2022
In women, fat oxidation during exercise changes with the menstrual cycle. This study aimed to investigate the effect of green tea extract (GTE) ingestion on fat oxidation during exercise depending on the menstrual cycle phase. Ten women with regular menstrual cycles participated in this randomized, double-blind, crossover study. GTE or placebo was administered during the menstrual cycle’s follicular phase (FP) and luteal phase (LP). Participants cycled for 30 min at 50% maximal workload, and a respiratory gas analysis was performed. Serum estradiol, progesterone, free fatty acid, plasma noradrenaline, blood glucose, and lactate concentrations were assessed before, during, and after the exercise. Fat oxidation, carbohydrate oxidation, and the respiratory exchange ratio (RER) were calculated using respiratory gas. Fat oxidation during the exercise was significantly higher in the FP than in the LP with the placebo (p < 0.05) but did not differ between the phases with GTE. Carbohydrate oxidation, serum-free fatty acid, plasma noradrenaline, blood glucose, and lactate concentrations were not significantly different between the phases in either trial. Our results suggest that GTE ingestion improves the decrease in fat oxidation in the LP.
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... xercise training performed at maximal fat oxidation intensity (FATmax) improves body composition, cardiorespiratory fitness, lipid profile, glucose homeostasis, and metabolic flexibility in subjects with obesity and diabetes type 2 (Chávez- Guevara et al., 2020). However, FATmax determination through indirect calorimetry (Amaro-Gahete et al., 2019;A. Jeukendrup & Achten, 2001) requires specialized and expensive equipment hindering FATmax assessment in a basic clinical setting. Therefore, alternative and costeffective methodological approaches are needed for optimizing exercise fat oxidation in people with obesity. ...
Association Among Different Aerobic Threshold Markers and FATmax in Men With Obesity
Article
Purpose: This work studies the interrelation of the first ventilatory threshold (VT1), the heart rate inflection point (HRIP), and the exercise intensity at which blood lactate started to accumulate (LIAB) or increased 1 mmol∙L-1 above baseline (LT+1.0); and examinee their association with the exercise intensity eliciting maximal fat oxidation (FATmax). Methods: Eighteen young men with obesity performed an incremental-load exercise test on a treadmill after overnight fasting. Gas exchange, heart rate, and blood lactate concentration were recorded. Linear regression analysis was used to determine the association among FATmax and AeT markers. A standard error of estimate (SEE) ≤9 beats∙min-1 and the concordance correlation coefficient (CCC) were used to examine the accuracy of different AeT for predicting FATmax heart rate. Results: The FATmax occurred at 36±7%VO2peak before the HRIP (41±6%VO2peak), LIAB (42±10%VO2peak), LT+1.0 (61±9%VO2peak) and VT1 (40±7%VO2peak). Furthermore, the HRIP (R2= 0.71; SEE= 6 beats∙min-1; CCC=0.77), VT1 (R2= 0.76; SEE= 5 beats∙min-1; CCC=0.84) and LIAB (R2= 0.77; SEE= 5 beats∙min-1; CCC=0.85) were strongly associated to FATmax and showed an acceptable estimation error for predicting FATmax heart rate. Otherwise, LT+1.0 showed a moderate correlation with FATmax, a low accuracy for predicting FATmax HR (R2= 0.57; SEE= 7 beats∙min-1; CCC=0.66) and a poor agreement with the rest of AeT markers (Bias: +20%VO2peak). Conclusion: The HRIP, LIAB and VT1 did not perfectly captured the FATmax, however, these could be exchanged for predicting the FATmax heart rate in men with obesity. Moreover, the LT+1.0 should not be used for AeT or FATmax assessment in men with obesity.
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... Again, due to other factors of fatigue and the unlikelihood of perfectly filled glycogen stores, the lower values are more realistic for common training scenarios. Especially long-distance runners and cyclists try to maximize the fat oxidation rate through very low training intensities (Jeukendrup and Achten, 2001). Due to the high utilization of CHO observed in our rowers, such a "FatMax" training is apparently unlikely to be realized even during low zone 1 rowing. ...
High Energetic Demand of Elite Rowing – Implications for Training and Nutrition
Article
Full-text available
  • Apr 2022
Purpose: Elite rowers have large body dimensions, a high metabolic capacity, and they realize high training loads. These factors suggest a high total energy requirement (TER), due to high exercise energy expenditure (EEE) and additional energetic needs. We aimed to study EEE and intensity related substrate utilization (SU) of elite rowers during rowing (EEE ROW ) and other (EEE NON-ROW ) training. Methods: We obtained indirect calorimetry data during incremental (N = 174) and ramp test (N = 42) ergometer rowing in 14 elite open-class male rowers (body mass 91.8 kg, 95% CI [87.7, 95.9]). Then we calculated EEE ROW and SU within a three-intensity-zone model. To estimate EEE NON-ROW , appropriate estimates of metabolic equivalents of task were applied. Based on these data, EEE, SU, and TER were approximated for prototypical high-volume, high-intensity, and tapering training weeks. Data are arithmetic mean and 95% confidence interval (95% CI). Results: EEE ROW for zone 1 to 3 ranged from 15.6 kcal·min ⁻¹ , 95% CI [14.8, 16.3] to 49.8 kcal·min ⁻¹ , 95% CI [48.1, 51.6], with carbohydrate utilization contributing from 46.4%, 95% CI [42.0, 50.8] to 100.0%, 95% CI [100.0, 100.0]. During a high-volume, a high-intensity, or a taper week, TER was estimated to 6,775 kcal·day ⁻¹ , 95% CI [6,651, 6,898], 5,772 kcal·day ⁻¹ , 95% CI [5,644, 5,900], or 4,626 kcal∙day ⁻¹ , 95% CI [4,481, 4,771], respectively. Conclusion: EEE in elite open-class male rowers is remarkably high already during zone 1 training and carbohydrates are dominantly utilized, indicating relatively high metabolic stress even during low intensity rowing training. In high-volume training weeks, TER is presumably at the upper end of the sustainable total energy expenditure. Periodized nutrition seems warranted for rowers to avoid low energy availability, which might negatively impact performance, training, and health.
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... The maximal fat oxidation rate (MFO) observed at submaximal exercise intensity during an incremental-load exercise test represents the capacity of the skeletal muscle to use fatty acids as a fuel when energy demand raises by muscle contraction (Fig. 1). Since introduced by Jeukendrup and Achten (2001), many studies have analyzed the validity of this parameter as a marker of metabolic flexibility and a predictor of sports performance in endurance athletes, reporting that (1) MFO is directly related to insulin sensitivity (r = 0.33, p < 0.01) and 24-h fat oxidation (r = 0.65, p < 0.01) in healthy males (Robinson et al. 2015); (2) predicts total fat oxidation during steady-state exercise in men with obesity (R 2 = 0.46, p < 0.01) (Chávez-Guevara et al. 2021) and is positively associated with exercise fat oxidation in the postprandial state in trained males (r = 0.83, p < 0.01) (Maunder et al. 2021); (3) is related with fat mass loss induced by exercise training performed at MFO intensity (FATmax) in subjects with obesity (r = 0.35, p < 0.01) (Drapier et al. 2018); (4) it explains 12 and 14% of endurance performance on Ironman (Frandsen et al. 2017) and ultra-trail male athletes, respectively (Martinez-Navarro et al. 2020). The aforementioned evidence highlights the relevance of investigating those biological and nutritional factors as well as the fitness components that determine MFO to understand the molecular and physiological mechanisms affecting metabolic health and athletic performance. ...
Biomarkers and genetic polymorphisms associated with maximal fat oxidation during physical exercise: implications for metabolic health and sports performance
Article
Full-text available
The maximal fat oxidation rate (MFO) assessed during a graded exercise test is a remarkable physiological indicator associated with metabolic flexibility, body weight loss and endurance performance. The present review considers existing biomarkers related to MFO, highlighting the validity of maximal oxygen uptake and free fatty acid availability for predicting MFO in athletes and healthy individuals. Moreover, we emphasize the role of different key enzymes and structural proteins that regulate adipose tissue lipolysis (i.e., triacylglycerol lipase, hormone sensitive lipase, perilipin 1), fatty acid trafficking (i.e., fatty acid translocase cluster of differentiation 36) and skeletal muscle oxidative capacity (i.e., citrate synthase and mitochondrial respiratory chain complexes II–V) on MFO variation. Likewise, we discuss the association of MFO with different polymorphism on the ACE, ADRB3, AR and CD36 genes, identifying prospective studies that will help to elucidate the mechanisms behind such associations. In addition, we highlight existing evidence that contradict the paradigm of a higher MFO in women due to ovarian hormones activity and highlight current gaps regarding endocrine function and MFO relationship.
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... Long distance triathlons and cycling competitions are gaining in popularity (Hadzipetros, 2009;Smale, 2016) and athletes are looking for ways to improve their performance, whether it is with a that carbohydrate is the ideal fuel for endurance events and high intensity exercise (Burke, 2010), it is interesting for an endurance athlete to increase their ability to oxidize lipids since the quantity of lipids in adipose tissue and in the muscles is considerably larger than the quantity of glycogen in the liver and the muscles (Gonzalez et al., 2016;Jensen et al., 2011;. A good fat oxidation capacity, combined with carbohydrate intake during endurance events, would allow an athlete to preserve more glycogen which can be used when the intensity increases, such as when a cyclist needs to respond to an acceleration or at the end of the race when the athletes are accelerating toward the finish line (Hall et al., 2016;Jeukendrup & Achten, 2001). Frandsen et al. (2017) found that the maximal fat oxidation of triathletes competing in an Ironman triathlon is related to their performance in this ultra-endurance event. ...
The Effects of Acute Ingestion of a High-fat Solution, compared to a High-Carbohydrate Solution, on Skeletal Muscle Oxygenation, Fat Oxidation and Performance During a 2-hour Cycling Effort Followed by a Short Time Trial in Cyclists and Triathletes
Article
Full-text available
  • Nov 2021
This study aimed to determine the effects of consuming a high fat solution (HFS) compared to a high carbohydrate solution (HCS) during a cycling effort on substrate oxidation, muscle oxygenation and performance with cyclists and triathletes. Thirteen men participated in this study (age: 30.4 ± 6.3 y; height: 178.7 ± 6.1 cm; weight: 74.9 ± 6.5 kg; V̇O2 peak: 60.5 ± 7.9 mlO2×kg-1×min-1). The solutions were isocaloric (total of 720 kcal) and were consumed every 20 minutes. Each solution of HFS contained 12.78 g of lipids, 1.33 g of carbohydrates and 0.67 g of proteins, and each solution of HCS contained 28 g of carbohydrates. We measured pulmonary oxygen consumption and skeletal muscle oxygenation, using a Near Infrared Spectrometer (NIRS) during a cycling effort consisting of 2 hours at 65 % of maximal aerobic power (MAP) followed immediately by a 3-minute time-trial (TT). We observed that the consumption of the HFS increased the rate of fat oxidation at the end of the sub-maximal effort (0.61 ± 0.14 vs 0.53 ± 0.17 g×min-1, p < 0.05). We have also shown that the HFS negatively affected the performance in the TT (mean Watts: HCS: 347.0 ± 77.4 vs HFS: 326.5 ± 88.8 W; p < 0.05) and the rating of perceived exertions during the sub-maximal effort (modified Borg Perceived Exertion scale: 1–10) (mean: 3.62 ± 0.58 for HCS vs 4.16 ± 0.62 for HFS; p < 0.05). We did not observe a significant effect of the acute consumption of the HFS compared to the HCS on muscle oxygenation during the cycling effort. Finally, we observed that cyclists who demonstrated a high skeletal muscle deoxygenation relative to their pulmonary oxygen consumption (DHHb/V̇O2) had a higher fat oxidation capacity (higher Fatmax). In conclusion, even though the consumption of HFS increased the rate of fat oxidation at the end of a sub-maximal effort, it did not affect muscle oxygenation and it negatively affected performance and perceived exertion during a time-trial and caused gastro-intestinal distress in some participants. Keywords: Fat oxidation, Skeletal muscle oxygenation, Lipid supplementation, Carbohydrate supplementation, Near Infrared Spectroscopy (NIRS), Cycling, Triathlon.
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A recommendation from The Centers for Disease Control and Prevention and the American College of Sports Medicine
Article
Full-text available
  • Mar 1995
OBJECTIVE--To encourage increased participation in physical activity among Americans of all ages by issuing a public health recommendation on the types and amounts of physical activity needed for health promotion and disease prevention. PARTICIPANTS--A planning committee of five scientists was established by the Centers for Disease Control and Prevention and the American College of Sports Medicine to organize a workshop. This committee selected 15 other workshop discussants on the basis of their research expertise in issues related to the health implications of physical activity. Several relevant professional or scientific organizations and federal agencies also were represented. EVIDENCE--The panel of experts reviewed the pertinent physiological, epidemiologic, and clinical evidence, including primary research articles and recent review articles. CONSENSUS PROCESS--Major issues related to physical activity and health were outlined, and selected members of the expert panel drafted sections of the paper from this outline. A draft manuscript was prepared by the planning committee and circulated to the full panel in advance of the 2-day workshop. During the workshop, each section of the manuscript was reviewed by the expert panel. Primary attention was given to achieving group consensus concerning the recommended types and amounts of physical activity. A concise \"public health message was developed to express the recommendations of the panel. During the ensuing months, the consensus statement was further reviewed and revised and was formally endorsed by both the Centers for Disease Control and Prevention and the American College of Sports Medicine. CONCLUSION--Every US adult should accumulate 30 minutes or more of moderate-intensity physical activity on most, preferably all, days of the weekType: CONSENSUS DEVELOPMENT CONFERENCEType: JOURNAL ARTICLEType: REVIEWLanguage: Eng
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Role of fat oxidation in long-term stabilization of body weight in obese women
Article
Full-text available
  • Apr 1992
Two studies were performed to investigate the association between body fat mass and fat oxidation. The first, a cross-sectional study of 106 obese women maintaining stable body weight, showed that these two variables were significantly correlated (r = 0.56, P less than 0.001) and the regression coefficient indicated that a 10-kg change in fat mass corresponded to a change in fat oxidation of approximately 20 g/d. The second, a prospective study, validated this estimate and quantifies the long-term adaptations in fat oxidation resulting from body fat loss. Twenty-four moderately obese women were studied under controlled dietary conditions at stable weight before and after mean weight and fat losses of 12.7 and 9.8 kg, respectively. The reduction in fat oxidation was identical to that predicted by the above regression. We conclude that changes in fat mass significantly affect fat oxidation and that this process may contribute to the long-term regulation of fat and energy balance in obese individuals.
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Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine
Article
  • Feb 1995
Objective: To encourage increased participation in physical activity among Americans of all ages by issuing a public health recommendation on the types and amounts of physical activity needed for health promotion and disease prevention. Participants: A planning committee of five scientists was established by the Centers for Disease Control and Prevention and the American College of Sports Medicine to organize a workshop. This committee selected 15 other workshop discussants on the basis of their research expertise in issues related to the health implications of physical activity. Several relevant professional or scientific organizations and federal agencies also were represented. Evidence: The panel of experts reviewed the pertinent physiological, epidemiologic, and clinical evidence, including primary research articles and recent review articles. Consensus process: Major issues related to physical activity and health were outlined, and selected members of the expert panel drafted sections of the paper from this outline. A draft manuscript was prepared by the planning committee and circulated to the full panel in advance of the 2-day workshop. During the workshop, each section of the manuscript was reviewed by the expert panel. Primary attention was given to achieving group consensus concerning the recommended types and amounts of physical activity. A concise "public health message" was developed to express the recommendations of the panel. During the ensuing months, the consensus statement was further reviewed and revised and was formally endorsed by both the Centers for Disease Control and Prevention and the American College of Sports Medicine. Conclusion: Every US adult should accumulate 30 minutes or more of moderate-intensity physical activity on most, preferably all, days of the week.
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Effects of long-term physical training on body fat, metabolism, and blood pressure in obesity
Article
Twenty-seven women with varying degrees of obesity were physically trained for 6 mo on an ad lib. diet. Body fat changes were positively correlated with the number of fat cells in adipose tissue. Obese women with fewer fat cells decreased in weight during training whereas women with severe obesity and an increased number of fat cells even gained weight. Blood pressure decreased consistently after training. Blood pressure elevation was not associated with body fat mass, nor was a decrease in blood pressure associated with a decrease in body fat or with pretraining blood pressure level. There were, instead, correlations between decreases in blood pressure on the one hand and initial concentrations and decreases in plasma insulin and triglycerides and blood glucose on the other. These results suggest an association between elevated blood pressure and metabolic variables. The possibility of treating and preventing early essential hypertension with methods that also correct the metabolic derangement, such as diet and exercise, should be given high priority in further research.
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Diminished plasma free fatty acid clearance in obese subjects
Article
Obese subjects were compared with lean subjects to define the previously reported disturbance of plasma free fatty acid (FFA) kinetics in terms of altered net transport (lipolysis) or clearance (esterification). These measurements were made during prolonged constant infusions of 1--14C-palmitate toward the end of sustained glucose ingestion and again 6-8 hr after stopping glucose. Net transport of FFA was suppressed to equally low levels in obese and lean subjects, though at the expense of higher insulin concentrations in the obese. Whereas in the lean subjects the clearance of FFA was significantly stimulated with glucose, the obese subjects showed low clearance rates both during and after stopping glucose. When glucose was stopped, net transport rose more rapidly and to a greater extent in some obese than in the lean subjects. The increased influx of FFA led to a rise in the plasma triglyceride level only in the lean subjects. These studies suggest that clearance of plasma FFA, probably denoting esterification in tissues such as muscle and adipose tissue, is impaired in obesity and cannot be readily stimulated with glucose and insulin. Lipolysis, measured as net transport of FFA, however, is suppressible with glucose and insulin in the obese, though this might be achieved only at insulin levels that are higher than those in lean subjects.
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Training induced adaptation of skeletal muscle and metabolism during submaxial exercise
Article
  • Oct 1977
1. Six subjects were trained using a one-leg bicycle exercise for 2 months. The untrained leg served as control. After the training period, muscle oxidative capacity, determined as succinate dehydrogenase activity, was 27% higher in the trained (as opposed to the control) leg (P < 0.05).2. When the subjects in this situation performed a 1 h two-legged submaximal bicycle exercise bout (150-225 W), determinations of V(O2) of the single leg (leg blood flow x (A-V)(O2) difference) revealed that they appeared to choose to work harder with their trained than with their untrained leg, so as to make the relative loads for the two legs the same.3. Determinations of O(2) and CO(2) on femoral arterial and venous blood demonstrated that the R.Q. was lower in the trained as compared to the untrained leg, 0.91 cf. 0.96 (10 min) and 0.91 cf. 0.94 (50 min) (P < 0.05).4. That metabolism of fat was more pronounced in the trained leg was further supported by the finding of a significant net uptake of free fatty acids in this leg only. Moreover, a lower release of lactate from the trained leg was demonstrated.5. It is suggested that the shift towards a more pronounced metabolism of fat in the trained leg is a function of an increased muscle oxidative capacity.
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Increased plasma FFA uptake and oxidation during prolonged exercise in trained vs. untrained humans
Article
We studied the effect of local muscle adaptations on free fatty acid (FFA) metabolism during prolonged exercise in trained and untrained subjects. Six trained (T) and six untrained (UT) young human males exercised for 3 h at 60% of their individual maximal dynamic knee extension capacity. The contribution of blood and plasma metabolites as well as intramuscular substrates to oxidative metabolism in the thigh was calculated from arteriovenous differences and femoral-venous blood flow as well as from muscle biopsies in subjects that were continuously infused with [1-14C]palmitate. Arterial plasma FFA concentration increased over time in both T and UT. Fractional uptake of FFA across the thigh remained unchanged over time in T (15%) but decreased in UT (from 15 to 7%), especially during the last hour of exercise. Thus FFA uptake increased linearly over time in T (96 +/- 20 to 213 +/- 20 mumol.min-1.kg-1), whereas it leveled off after 2 h in UT (74 +/- 16 to 133 +/- 46) even though FFA delivery increased similarly in T and UT. Percentage oxidation was similar in T and UT; thus total FFA oxidation was higher in T. Glucose uptake increased in both groups over time and was significantly higher in UT during the last hour of exercise. In conclusion, during prolonged knee extension exercise, FFA uptake increases linearly with FFA delivery in the trained thigh, whereas in the untrained thigh uptake becomes saturated with time. This difference partly explains the increased lipid oxidation in T vs. UT and suggests, furthermore, that local muscle adaptations to training are important for the utilization of FFA during prolonged exercise.
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Effect of insulin on oxidative and nonoxidative pathways of free fatty acid metabolism in human obesity
Article
The dose-response relationship between the plasma insulin concentration and oxidative and nonoxidative pathways of free fatty acid (FFA) metabolism was examined in 11 obese and 7 lean subjects using a stepwise insulin clamp technique in combination with indirect calorimetry and infusion of [1-14C]palmitate. The fasting plasma FFA concentration was elevated in obese subjects (793 +/- 43 vs. 642 +/- 39 mumol/l; P less than 0.01) and was associated with an increased basal rate of plasma FFA turnover, FFA oxidation, and nonoxidative FFA disposal, i.e., reesterification (all P less than 0.01). Suppression of plasma FFA turnover by physiological increments in plasma insulin was impaired in obese compared with lean subjects. However, plasma FFA turnover expressed per kilogram fat mass was normally suppressed by insulin in obese subjects. Although insulin suppressed plasma FFA oxidation to the same extent in lean and obese subjects, inhibition of total lipid oxidation by insulin was impaired in the obese group. Obese subjects had an enhanced basal rate of nonoxidative FFA disposal, which was suppressed less by physiological increments in plasma insulin compared with lean controls. Therefore, we conclude that 1) lipolysis in uncomplicated obesity is normally sensitive to insulin; the enhanced FFA flux is simply a consequence of the increased fat mass. 2) Nonoxidative FFA disposal expressed per lean body mass is enhanced in obese subjects and correlates with the increase in plasma FFA concentration and fat mass. 3) Enhanced oxidation of intracellular lipids contributes to the enhanced rate of total lipid oxidation in obese subjects.
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