[Show abstract][Hide abstract] ABSTRACT: The objective was to investigate the effects of a 3- week weight-management program including moderate energy restriction and exercise training at 2 intensities [low intensity (LI): 40% and high intensity (HI): 70% maximal oxygen uptake (V'O(2)max)] on body composition, energy expenditure, and fat oxidation rate in severely obese adolescents. Twenty obese adolescents, aged 15-17 yr (body mass index: 37.5 kg/m(2); 38.2% fat mass) participated in this study. Before starting (week 0, W0) and at the end of the weight-management period (week 3,W3), body composition was assessed by a multifrequency tetrapolar impedancemeter; basal metabolic rate (BMR), energy expenditure, and substrate oxidation rate during exercise and post-exercise recovery by indirect calorimetry. At W3, body mass and fat mass decreased significantly (p<0.005) in all groups, and the decreases were significantly greater in the LI than in the HI group (-8.1±1.6 vs -5.9±1.6 kg and -4.2±1.9 vs -2.3±1.7 kg, p<0.05, respectively). Predicted V'O(2)max, expressed in relative values, changed significantly only in the HI group by +0.010±0.006 l/(kg fat-free mass × min) (p=0.010). By contrast, no significant changes were observed at W3 in BMR, energy expenditure, and substrate oxidation rate during exercise and post-exercise recovery. In conclusion, LI (40% of V'O(2)max) physical activity favors fat oxidation and it seems advisable to encourage obese adolescents to perform LI physical activity which is more feasible and acceptable than intense exercise.
[Show abstract][Hide abstract] ABSTRACT: A functional evaluation of skeletal muscle oxidative metabolism was performed in a group of obese adolescents (OB). The various components of pulmonary O(2) uptake (Vo(2)) kinetics were evaluated during 10-min constant-load exercises (CLE) on a cycloergometer at different percentages of Vo(2max). The relationships of these components with the gas exchange threshold (GET) were determined. Fourteen male OB [age 16.5 ± 1.0 (SD) yr, body mass index 34.5 ± 3.1 kg·m(-2)] and 13 normal-weight, age-matched nonathletic male volunteers (control group) were studied. The time-constant (τf) of the fundamental component and the presence, pattern, and relative amplitude of the slow component of Vo(2) kinetics were determined at 40, 60, and 80% of Vo(2max), previously estimated during an incremental test. Vo(2max) (l/min) was similar in the two groups. GET was lower in OB (55.7 ± 6.7% of Vo(2max)) than in control (65.1 ± 5.2%) groups. The τf was higher in OB subjects, indicating a slower fundamental component. At CLE 60% (above GET in OB subjects, below GET in control subjects) a slow component was observed in nine out of fourteen OB subjects, but none in the control group. All subjects developed a slow component at CLE 80% (above GET in both OB and control). Twelve OB subjects did not complete the 10-min CLE 80% due to voluntary exhaustion. In nine OB subjects, the slow component was characterized by a linear increase in Vo(2) as a function of time. The slope of this increase was inversely related to the time to exhaustion. The above findings should negatively affect exercise tolerance in obese adolescents and suggest an impairment of skeletal muscle oxidative metabolism. Also in obese adolescents, exercise evaluation and prescription at submaximal loads should be done with respect to GET and not at a given percentage of Vo(2max).
[Show abstract][Hide abstract] ABSTRACT: Physical activity is essential in obesity management because of the impact of exercise-related energy expenditure (EE) and fat oxidation (Fox) rate on a daily balance, but the specific physiological effects of different exercise modalities are scarcely known in obese individuals. The objective of the study was to compare the metabolic responses to treadmill (TM) and cycle ergometer (CE) exercise in obese adolescents. Gas exchange, heart rate (HR), blood lactate (LA) concentration, EE and Fox were determined at different intensity levels (up to about 85% of maximal oxygen uptake) during TM and CE in 14 pubertal (Tanner stage: >3) obese (BMI SDS: 2.15-3.86) male adolescents (age: 13-18 years). At comparable HR, oxygen uptake, EE and Fox were higher, and LA lower, during TM than CE (P<0.05-0.001), suggesting that cycling imposes a metabolic involvement at the level of the single active muscles greater than walking. Therefore, due to different physiological responses to TM and CE, walking was more convenient than cycling in obese adolescents, permitting to attain the same EE at lower HR, with lower blood LA concentration and with greater Fox. These conclusions seem clinically relevant when using exercise as a part of multidisciplinary treatment for juvenile obesity and amelioration of related metabolic disturbances.
Scandinavian Journal of Medicine and Science in Sports 09/2010; 20(4):630-7. DOI:10.1111/j.1600-0838.2009.00975.x · 3.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The objective is to study the effects of low-intensity (LI) or high-intensity (HI) equicaloric exercises on energy expenditure (EE) and substrate oxidation rate during and after the exercises in severely obese Caucasian adolescents. Twenty obese boys (BMI-SDS 3.04 +/- 0.52, %Fat Mass 38.2 +/- 2.1%) aged 14-16 years (pubertal stage >3) participated in this study. Maximal oxygen uptake (V'O(2max)) and maximal fat oxidation rate were determined with indirect calorimetry using a graded exercise test on a treadmill. EE and substrate oxidation rate during equicaloric low-intensity (LI, 42% V'O(2max) for 45 min) and high-intensity (HI, 67% V'O(2max) for 30 min) exercises on a treadmill and during post-exercise recovery period (60 min) were determined with indirect calorimetry. Maximal fat oxidation rate was observed at 42 +/- 6% V'O(2max) (62 +/- 5% HR(max)) and fat oxidation rate was 0.45 +/- 0.07 g/min. The total amounts of EE, during the LI and HI exercises, and the post-exercise recovery periods were not significantly different (1,884 +/- 250 vs. 1,973 +/- 201 kJ, p = 0.453), but the total amount of fat oxidised was significantly higher (+9.9 g, +55.7%, p < 0.001) during the LI exercise than during the HI exercise. However, fat oxidation rates during the post-exercise recovery periods were not significantly different following LI and HI exercises. Total fat oxidised was significantly higher during the LI than during the HI exercise in obese adolescents. However, the equicaloric exercise intensity did not influence EE, fat and carbohydrate oxidation rate during the recovery period.
[Show abstract][Hide abstract] ABSTRACT: The objective of the present study was to explore the relationship between basal metabolic rate (BMR), gender, age, anthropometric characteristics, and body composition in severely obese white subjects. In total, 1,412 obese white children and adolescents (BMI > 97 degrees percentile for gender and age) and 7,368 obese adults (BMI > 30 kg/m(2)) from 7 to 74 years were enrolled in this study. BMR was measured using an indirect calorimeter equipped with a canopy and fat free mass (FFM) were obtained using tetrapolar bioelectrical impedance analysis (BIA). Using analysis of covariance, we tested the effect of gender on the relationship between BMR, age, anthropometry, and body composition. In children and adolescents, the predictor x gender interaction was significant in all cases except for FFM x gender. In adults, all predictor x gender interactions were significant. A prediction equation based on body weight (BW), age, and gender had virtually the same accuracy of the one based on FFM, age, and gender to predict BMR in both children and adults (R(2)(adj) = 0.59 and 0.60, respectively). In conclusion, gender was a significant determinant of BMR in children and adolescents but not in adults. Our results support the hypothesis that the age-related decline in BMR is due to a reduction in FFM. Finally, anthropometric predictors of BMR are as accurate as body composition estimated by BIA.
[Show abstract][Hide abstract] ABSTRACT: In order to assess the energy cost of cycling and aerobic capacity in juvenile obesity, responses to cycle ergometer exercise were studied in 10 pubertal obese (OB) [body mass index (BMI) SD score (SDS): 3.40+/-0.58 SD] adolescent girls (age: 16.0+/-1.2 yr) and in 10 normal-weight (NW, BMI SDS: -0.30+/-0.54) girls of the same age (15.1+/-1.9). To this aim, gas exchange, heart rate (HR), and energy expenditure (EE) were studied during graded cycle ergometer test at 40, 60, 80, 100, and 120 W. The energy cost of cycling was higher in OB, being oxygen uptake (VO2) higher (about 20%) in OB than in NW girls at all workloads (p<0.01-0.001). Estimated maximal VO2 and VO2 at anaerobic threshold were significantly (p<0.05) higher in OB girls [although lower per unit body mass (p<0.01) and similar for unit fat-free mass], and explained the higher oxygen pulse and lower HR for any EE observed during submaximal exercise in OB. While net mechanical efficiency (ME) was significantly lower in OB (p<0.01), delta ME was similar in both groups, indicating no substantial derangement of muscle intrinsic efficiency. It is concluded that, despite a higher cost of cycling, OB girls can rely on a larger aerobic capacity which makes them able to sustain this kind of exercise within a wide range of work loads, with relevant implications when planning protocols of physical activity in the context of interventions for the reduction of juvenile obesity.
[Show abstract][Hide abstract] ABSTRACT: The physical activity ratio (PAR) values are commonly used to convert subjects' physical activity recalls into estimates of daily energy expenditure (DEE). A PAR is defined as the ratio between energy expenditure corresponding to a sedentary or a physical activity (kJ/min) and basal metabolic rate [(BMR) kJ/min]. The objective of the present study was to determine the PAR for different sedentary and physical activities in obese adolescents. Thirty-three obese adolescents [mean body mass index: 35.1 kg/m2; 40.3 % fat mass] aged 11 to 17 yr participated in this study. BMR was assessed by indirect calorimetry after an overnight fast by means of an open-circuit, indirect computerised calorimetry with a rigid, transparent, ventilated canopy. Energy expenditures corresponding to various sedentary and physical activities in free-living conditions were determined using a portable metabolic unit, and body composition by bioelectrical impedance analysis (BIA). The PAR of each activity was obtained by dividing the assessed energy expenditure by BMR. In this study, the PAR of various sedentary and physical activities did not vary significantly with sex, age, and body mass. Thus, the data for boys and girls were combined and the PAR for 27 sedentary and physical activities were determined. The PAR values can be applied to determine the mean DEE (kJ) using the specific equation considering BMR (kJ/min), PAR, and duration (min) of each activity performed by the subject during the 24 h. This information will be useful to health-care professionals because estimation of DEE in obese adolescents is necessary in order to prescribe an adequate dietary therapy to induce a desired level of energy deficit.
[Show abstract][Hide abstract] ABSTRACT: Physical activity is essential in obesity management, but exercise capacity is compromised in obese individuals due to the excessive body mass, impacting on body movement's energetics, and to the dysfunctions of regulatory mechanisms, affecting cardiovascular responses. This study aims to compare the energetics and cardiovascular responses of walking and cycling in obese women, and to formulate recommendations regarding the most suitable type of exercise for obesity. Fifteen obese (OB) and six normal weight (NW) women exercised on treadmill (TM) and cycle ergometer (CE). During both exercise modalities, metabolic rate was higher in OB than in NW and correlated with measures of body mass. Leg movement metabolic rate during cycling depended upon individual adiposity, and when accounted for, mechanical efficiency was similar in the two groups. When accounting for extra mass, differences in metabolic rate among groups are abolished for CE, indicating no obesity impairment of muscle efficiency, but not for TM, suggesting that differences in biomechanics may explain the higher net cost of transport of OB. In both groups, HR was higher during CE than TM at the same oxygen uptake (VO(2)), but in OB the HR increment over VO(2) was greater for CE than for TM. Therefore, due to different cardiovascular responses to TM and CE in OB, walking is more convenient, enabling OB to attain target energy expenditure at lower HR or in a shorter time.
[Show abstract][Hide abstract] ABSTRACT: Growth hormone (GH) replacement in adult GH-deficient (GHD) patients is reported to have a long-term beneficial effect on muscle mass and function, these effects being greater in young males and in adult-onset compared with those with childhood-onset GHD. To date, more discordant data are reported on the degree of muscle impairment in untreated GHD patients, due to the large heterogeneity of this syndrome.
Muscle maximum total isotonic strength (ST), lower limb maximum power output (W), maximum aerobic capacity (VO(2)max) and body composition (by tetrapolar bio-impedentiometry) were evaluated in seven short-stature adults with childhood-onset GHD and in seven age-matched normal-stature controls with comparable lifestyle and daily physical activity.
Significant differences were found in body composition between control subjects and GHD patients, who presented higher adiposity (mean BMI+/-SD: GHD, 27.8+/-5.8 kg/m(2); controls, 22.1+/-0.8 kg/m(2); p=0.047), larger fat mass (GHD, 21.8+/-10.7 kg; controls, 8.8+/-3.5 kg; p=0.008), and lower fat-free mass (GHD, 65.8+/-11.4 %; controls, 87.0+/-6.5 %; p=0.002). In absolute terms, GHD patients attained significantly lower values in ST (GHD, 2479+/-493 N; controls, 4578+/-1476 N; p=0.008), W (GHD, 1092+/-452 W; controls, 1910+/-781 W; p=0.035) and VO(2)max (GHD, 1.68+/-0.40 l/min; controls, 2.67+/-0.84 l/min; p=0.035) than those attained by controls. The differences were still evident when the results were normalized by unit body mass, whereas they disappeared when the parameters were expressed per unit fat-free mass, suggesting for these patients the presence of an intrinsic muscle function in the same range as that of control subjects.
Middle-aged and short-stature adults with childhood-onset GHD, who received discontinuous pit-GH substitution therapy only during childhood and have uncorrected long-lasting GHD, still retain a normal intrinsic muscle capability in attaining isotonic strength, generating anaerobic power as well as accomplishing oxidative processes. Nonetheless, it is not known which age-dependent evolution in motor dysfunction could be expected in this subgroup of GHD patients, when ageing processes add up to hormonal deficiencies.
Archives of Medical Research 02/2008; 39(1):78-83. DOI:10.1016/j.arcmed.2007.06.011 · 2.41 Impact Factor