HOW MUCH PHYSICAL-ACTIVITY IS NEEDED TO MINIMIZE WEIGHT-GAIN IN PREVIOUSLY OBESE WOMEN

Exercise is frequently identified as a predictor of weight maintenance after elective weight loss in retrospective studies of treatments for obesity. We conducted a prospective study to test whether physical ac tivity measured soon after weight loss predicted weight maintenance an d to determine how much physical activity was required to optimize mai ntenance. Thirty-two women [mean (+/- SD) age, 38 +/- 7 y; body mass i ndex (in kg/m(2)), 24 +/- 3] were recruited through local advertising within 3 mo of reaching their target for weight loss (23 +/- 9 kg). To tal energy expenditure (TEE) was measured by the doubly labeled water method. Postabsorptive resting metabolic rate (RMR)and postprandial RM R [expressed as thermic effect of a meal (TEM)] were measured by respi ratory gas exchange. Women in the physically active, group (ratio of T EE to RMR = 1.89 +/- 0.08) gained 2.5 +/- 3.1 kg during the 12 mo afte r reaching their target for weight loss, moderately active women (TEE: RMR = 1.64 +/- 0.05) gained 9.9 +/- 10.5 kg, and sedentary women (TEE: RMR = 1.44 +/- 0.08) gained 7.0 +/- 5.9 kg (P < 0.01). Retrospective a nalyses of weight regain as a function of energy expended in physical activity indicated a threshold for weight maintenance of 47 kJ.kg body wt(-1).d(-1). This corresponds to an average of 80 min/d of moderate activity or 35 min/d of vigorous activity added to a sedentary lifesty le.