Baseline Habitual Physical Activity Predicts Weight Loss, Weight Compensation, and Energy Intake During Aerobic Exercise

Objective This study aimed to determine whether different measures of habitual physical activity (PA) at baseline predict weight change, weight compensation, and changes in energy intake (EI) during a 24-week supervised aerobic exercise intervention. Methods Data from 108 participants (78 women; 48.7 [SD: 11.6] years; BMI 31.4 [SD: 4.6] kg/m(2)), randomly assigned to either the moderate-dose exercise group (8 kcal/kg of body weight per week) or the high-dose exercise group (20 kcal/kg of body weight per week) of the Examination of Mechanisms of Exercise-induced Weight Compensation (E-MECHANIC) trial, were analyzed. Moderate-to-vigorous PA (MVPA), steps per day, and PA energy expenditure (PAEE) were measured with SenseWear armbands (BodyMedia, Pittsburgh, Pennsylvania), and total activity energy expenditure and EI were estimated with doubly labeled water, all over 2 weeks, before and toward the end of the intervention. Multiple linear regression models, adjusted for sex, exercise group, and baseline value of the outcome, were used. Results Baseline habitual MVPA levels predicted weight change (beta = -0.275; P = 0.020), weight compensation (beta = -0.238; P = 0.043), and change in EI (beta = -0.318; P = 0.001). Associations between baseline PAEE and outcomes were comparable, whereas steps per day and, importantly, total activity energy expenditure (via doubly labeled water) did not significantly predict change in weight-related outcomes. Conclusions While acknowledging substantial variability in the data, on average, lower baseline habitual MVPA and PAEE levels were associated with less weight loss from exercise, higher compensation, and increased EI.