Effect of Physical Activity on Weight Loss, Energy Expenditure, and Energy Intake During Diet Induced Weight Loss

Objective: Objective measurements of physical activity (PA), energy expenditure (EE) and energy intake can provide valuable information regarding appropriate strategies for successful sustained weight loss. Design and Methods: The total EE was examined by doubly labeled water, resting metabolic rate by indirect calorimetry, PA with activity monitors, and energy intake by the intake/balance technique in 116 severely obese undergoing intervention with diet alone (DO) or diet plus PA (D-PA). Results: Weight loss of 9.6 +/- 6.8 kg resulted in decreased EE which was not minimized in the D-PA group. Comparing the highest and lowest quartiles of increase in PA revealed a lower decrease in TDEE (-122 +/- 319 vs. -376 +/- 305 kcal day(-1)), elimination of the drop in AEE (83 +/- 279 vs. -211 +/- 284 kcal day(-1)) and greater weight loss (13.0 +/- 7.0 vs. 8.1 +/- 6.3 kg). Increased PA was associated with greater adherence to energy restriction and maintenance of greater weight loss during months 7-12. Conclusion: Noncompliance to prescribed PA in the DO and D-PA groups partially masked the effects of PA to increase weight loss and to minimize the reduced EE. Increased PA was also associated with improved adherence to prescribed caloric restriction. A strong recommendation needs to be made to improve interventions that promote PA within the context of behavioral weight loss interventions.