The Effect of Acute Energy Deprivation on Metabolic Measures during Exercise and at Rest in Physically Active Adults.

Abstract

Endurance athletes often consume fewer calories than required to support energy needs and optimize performance. However, few studies have investigated how energy deprivation impacts the metabolic response to exercise. PURPOSE: This investigation characterized the effects of an acute period of energy deprivation on resting energy expenditure (REE), respiratory quotient (RQ), substrate oxidation, and respiratory exchange ratio (RER) in normal weight, physically active adults. METHODS: Physically active men (n=8, 22 y, 73.6 kg, 174.2 cm, 14% body fat, VO2peak= 57.3 mL•kg−1•min−1) and women (n=7, 21 y, 64.5 kg, 166.1 cm, 29% body fat, VO2peak= 46.7 mL•kg−1•min−1) were studied following 7 days of reduced calorie intake (~85% of estimated energy needs) for which protein intake was 1.5 g−1•kg−1•d−1 and 30% of total calories were from fat. RER was measured during a 45 min run at 65% VO2peak. REE, RQ, and substrate oxidation were assessed at rest via indirect calorimetry. RESULTS: Average weight loss was 1.6 kg (p<0.001). No differences were identified in RER, REE, RQ or substrate oxidation in response to the short-term energy restriction period. However, differences were noted at rest for RQ (0.86 ± 0.01 vs 0.82 ± 0.01, p<0.05) and carbohydrate oxidation (44% ± 2 vs 31% ± 3, p<0.05) for men and women, respectively. CONCLUSIONS: These data indicated that an acute period of moderate energy deprivation did not impact metabolic responses to an endurance exercise bout in physically active adults; but elicited different responses in RQ and substrate oxidation between men and women at rest.