Percentage Of Energy Expenditure Research Articles

Effects of chronic decaffeinated green tea extract supplementation on lipolysis and substrate utilization during upper body exercise

BackgroundDecaffeinated green tea extract (dGTE) can increase fat oxidation during leg exercise, but dGTE is unsuitable for many people (e.g., those with injuries/disabilities), and its effects on arm exercise and women are unknown. MethodsEight adults (23–37 years old, 4 women) performed an incremental arm cycle test to measure peak oxygen uptake (VO2peak), followed by four 1-h trials at 50% VO2peak. Subjects were randomly assigned to 650 mg of dGTE or placebo (PLA) for 4 weeks followed by a 4-week washout and crossover trial. Blood samples were obtained pre-exercise and post-exercise for glycerol and free fatty acid analysis. Respiratory gases were collected continuously. ResultsVO2 showed no differences across trials ((0.83–0.89) ± (0.19–0.25) L/min, p = 0.460), neither did energy expenditure ((264–266) ± (59–77) kcal, p = 0.420) nor fat oxidation (dGTE = 0.11 to 0.12 g/min vs. PLA = 0.10 to 0.09 g/min, p = 0.220). Fat oxidation as percentage of energy expenditure was not different for dGTE vs. PLA (23% ± 12% to 25% ± 11% vs. 23% ± 10% to 21% ± 9%, p = 0.532). Glycerol concentration increased post-exercise in all trials, independent of treatments (pre = (3.4–5.1) ± (0.6–2.6) mg/dL vs. post = (7.9–9.8) ± (2.6–3.7) mg/dL, p = 0.867, η2 = 0.005 for interaction), as did free fatty acid ((3.5–4.8) ± (1.4–2.2) mg/dL vs. (7.2–9.1) ± (2.6–4.5) mg/dL, p = 0.981, η2 = 0.000). ConclusionChronic dGTE supplementation had no effect on lipolysis and fat oxidation during arm cycle exercise in men and women.

Basal and Insulin Mediated VLDL-Triglyceride Kinetics in Type 2 Diabetic Men

OBJECTIVEIncreased very-low-density lipoprotein triglycerides (VLDL-TG) concentration is a central feature of diabetic dyslipidemia. The objective was to compare basal and insulin mediated VLDL-TG kinetics, oxidation, and adipose tissue storage in type 2 diabetic and healthy (nondiabetic) men.RESEARCH DESIGN AND METHODSEleven type 2 diabetic and 11 healthy men, matched for BMI and age, were included. Ex vivo-labeled VLDL-TG tracers, blood and breath samples, fat biopsies, indirect calorimetry, and body composition measures were applied to determine VLDL-TG kinetics, VLDL-TG fatty acids (FA) oxidation, and storage in regional adipose tissue before and during a hyperinsulinemic euglycaemic clamp.RESULTSVLDL-TG secretion was significantly greater in diabetic compared with healthy men (basal: 86.9 [31.0] vs. 61.9 [30.0] μmol/min, P = 0.03; clamp: 60.0 [26.2] vs. 34.2 [17.9] μmol · min−1, P = 0.01). The insulin mediated suppression of VLDL-TG secretion was significant in both groups. VLDL-TG clearance was lower in diabetic men (basal: 84.6 [32.7] vs. 115.4 [44.3] ml · min−1, P = 0.08; clamp: 76.3 [30.6] vs. 119.0 [50.2] ml · min−1, P = 0.03). During hyperinsulinemia fractional VLDL-TG FA oxidation was comparable, but in percentage of energy expenditure (EE), significantly higher in diabetic men. Basal VLDL-TG storage was similar, but significantly greater in abdominal compared with leg fat.CONCLUSIONSIncreased VLDL-TG in type 2 diabetic men is caused by greater VLDL-TG secretion and less so by lower VLDL-TG clearance. The ability of hyperinsulinemia to suppress VLDL-TG secretion appears preserved. During hyperinsulinemia VLDL-TG FA oxidation is significantly increased in proportion of EE in type 2 diabetic men. Greater basal abdominal VLDL-TG storage may help explain the accumulation of upper-body fat in insulin-resistant individuals.

Influence of age and pubertal status on substrate utilization during exercise with and without carbohydrate intake in healthy boys

Substrate utilization during exercise is known to differ between children and adults, but whether these differences are related to pubertal status is unclear. The objective of this study was to investigate the effects of pubertal status on endogenous (CHOendo) and orally ingested exogenous (CHOexo) carbohydrate and fat oxidation rates during exercise. Twenty boys at the same chronological age (12 y) were divided into three pubertal groups (pre-pubertal, PP: n=7; early-pubertal, EP: n=7; mid- to late-pubertal, M-LP: n=6) and consumed either a placebo or 13C-enriched 6% CHO drink while cycling for 60 min at approximately 70% of their maximal aerobic power (VO2 max). Another group of 14-year-old boys (pubertal, n=9) completed all procedures. Substrate utilization was calculated for the final 15 min of exercise using indirect calorimetry and stable isotope methodology. CHOexo decreased fat (p<0.001) and increased total CHO (p<0.001) oxidation, irrespective of group. Fat oxidation was higher (p=0.01) in younger boys than in older boys, but similar (p>or=0.33) among PP, EP, and M-LP boys. CHOexo contributed to approximately 30% of energy expenditure (EE) in PP and EP, but to only 24% in M-LP (p=0.02), which was identical to the older boys (24%). CHOexo oxidation rate as a percentage of EE was inversely related to testosterone levels (r=-0.51, p=0.005, n=29). It was concluded that reliance on CHOexo during exercise is particularly sensitive to pubertal status, with the highest oxidation rates observed in pre- and early-pubertal boys, independent of chronological age.

Fat oxidation at different intensities in wheelchair racing

Determination of fat oxidation at three different intensities in trained wheelchair athletes on the treadmill. The aim of the study was to assess the level and highest rate of fat oxidation in endurance-trained wheelchair athletes for recommendation on endurance training. Institute of Sports Medicine, Swiss Paraplegic Centre, Nottwil, Switzerland. Nine (seven men and two women) endurance-trained wheelchair athletes (VO(2peak) 40.2+/-6.7 ml/kg/min) were studied over 20 min at 55, 65 and 75% VO(2peak) on a treadmill in their own racing wheelchairs in order to find the exercise intensity with the highest absolute fat oxidation. As presumed, total energy expenditure for wheelchair racing was highest at 75% VO(2peak), while absolute fat oxidation was statistically not significantly different at the three tested intensities. Percentage of energy expenditure from fat oxidation decreased with increasing intensity from 31.4% at 55% VO(2peak) to 20.9% at 75% VO(2peak), while percentage from carbohydrate oxidation increased from 68.6% at 55% VO(2peak) to 79.1% at 75% VO(2peak). For wheelchair athletes, we recommend training of fat metabolism for endurance exercise at an intensity of 55% VO(2peak), because absolute fat metabolism is not higher at higher intensities but less carbohydrates are used at lower intensity levels. At lower intensities, exercise can be performed over a longer time before the emptied glycogen stores will limit exercise duration. This may apply especially to paraplegic subjects whose active muscle mass is limited in contrast to able-bodied athletes.