Influence of ascorbic acid on the thermic effect of feeding in overweight and obese adult humans.
The thermic effect of feeding (TEF: increase in energy expenditure following acute energy intake) is an important physiological determinant of total daily energy expenditure and thus energy balance. Approximately 40% of TEF is believed to be mediated by sympathoadrenal activation and consequent beta-adrenergic receptor stimulation of metabolism. In sedentary adults, acute administration of ascorbic acid, a potent antioxidant, augments the thermogenic response to beta-adrenergic stimulation. We hypothesized that acute ascorbic acid administration augments TEF in sedentary overweight and obese adults. Energy expenditure was determined (ventilated hood technique) before and 4 h after consumption of a liquid-mixed meal (caloric equivalent 40% of resting energy expenditure (REE)) in 11 sedentary, overweight/obese adults (5 men, 6 women; age: 24 +/- 2 years; BMI: 28.5 +/- 1.0 kg/m(2) (mean +/- s.e.)) on two separate, randomly ordered occasions: during continuous intravenous administration of saline (placebo control) and/or ascorbic acid (0.05 g/kg fat-free mass). Acute ascorbic acid administration prevented the increase in plasma concentration of oxidized low-density lipoprotein in the postprandial state (P = 0.04), but did not influence REE (1,668 +/- 107 kcal/day vs.1,684 +/- 84 kcal/day; P = 0.91) or the area under the TEF response curve (33.4 +/- 2.4 kcal vs. 30.5 +/- 3.6 kcal; P = 0.52) (control vs. ascorbic acid, respectively). Furthermore, acute ascorbic acid administration had no effect on respiratory exchange ratio, heart rate, or arterial blood pressure in the pre- and postabsorptive states (all P > 0.64). These data imply that the attenuated TEF commonly observed with sedentary lifestyle and obesity is not modulated by ascorbic acid-sensitive oxidative stress.
Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA.
Sean A
SA
Newsom
Roger J
RJ
Paxton
Grant M
GM
Rynn
Christopher
C
Bell
D000293:Adolescent; D000328:Adult; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D002149:Energy Intake / Q000187:drug effects* / Q000502:physiology; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000378:metabolism / Q000503:physiopathology*; D050177:Overweight / Q000378:metabolism / Q000503:physiopathology*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D012146:Rest / Q000502:physiology; D016037:Single-Blind Method
D000975:Antioxidants; D001205:Ascorbic Acid