Energy expenditure at rest and during exercise in nonobese female cyclical dieters and in nondieting control subjects

Abstract

The purpose of this research was to determine if resting energy expenditure (REE) and exercise energy expenditure (EEE) differed between nonobese female cyclical dieters (n = 11) and nondieting control subjects (n = 12). Dieters were defined as having intermittent periods of caloric restriction (less than or equal to 4184 kJ/d, or less than or equal to 1000 kcal/d) for greater than or equal to 7-10 d four times in the preceding year. Dieters were significantly (P less than 0.01) heavier (66 vs 57 kg) and fatter (26% vs 21% body fat) than controls subjects whereas fat-free tissue was similar in both groups. Dieters had significantly (P less than 0.003) lower relative REE than did control subjects (2.8 vs 3.1 mL O2.kg-1.min-1; 79 vs 92 kJ.kg body wt-1.d-1, or 19 vs 22 kcal.kg body wt-1.d-1) but absolute REE (kJ/d, or kcal/d) was similar. Regardless of the workload examined, relative EEE was significantly (P less than 0.009) lower in dieters than in control subjects whereas absolute EEEs were similar at each workload. Results indicate an increased efficiency of food utilization during exercise in dieters but no difference in absolute REE. In addition, repeated bouts of dieting may alter body composition.