The Intraday Relation Between Physical Activity and Dietary Intake Among Behavioral Weight Loss Participants
Authors:   , Crochiere Rebecca Jane , Forman Evan M 
Published: July 2022

Weight control (weight loss/maintenance) is determined by energy balance, i.e., the difference between energy intake (from food and beverage consumption) and energy expenditure (from resting metabolic rate and physical activity [PA]). Energy balance typically is most strongly influenced by energy intake (as compared to PA), and it remains unknown whether engaging in PA, a central component of most behavioral weight loss programs, increases, decreases, or has no effect on same-day energy intake among individuals with overweight/obesity pursuing weight loss. Findings from the extant literature in this area are mixed, and more importantly, the methodology and design of existing studies (e.g., using healthy-weight samples, laboratory-based settings, and correlation designs that lack temporal precedent) make their findings inapplicable to the current research question. The current study addressed this gap in the literature by using technology that can measure PA and diet in individuals' every-day lives to examine how engaging in PA is associated with same-day energy intake among behavioral weight loss participants. Participants were 101 adults with overweight/obesity enrolled in a weight loss program instructed to follow a reduced-calorie diet and PA prescription. At mid-treatment, PA was measured via a wrist-worn accelerometer (Fitbit Charge) and dietary intake via a self-monitoring app (MyFitnessPal Premium) for 3 weeks. Multilevel models were used to examine the within-person, intraday relations between PA and dietary intake, including energy, macronutrient, and sugar intake. Specifically, the current study examined the relation between PA and the dietary intake preceding PA ("pre-PA"), acutely following PA ("acute post-PA," i.e., in the 2 hours following PA), in the remaining time in day following the acute post-PA period ("remaining time in day"), and across entire PA days ("full-day"), relative to non-PA matched time periods. Two definitions of PA were used, moderate-to-vigorous PA (MVPA) and any-intensity PA, which includes light, moderate, and vigorous PA. Primary aims showed energy intake was higher in the acute post-PA period (for MVPA only) but lower in the remaining time in day (both MVPA and any-intensity PA) relative to non-PA matched time periods. Energy intake also was higher in the pre-PA period (both MVPA and any-intensity PA), though there was no difference in full-day energy intake on entire PA days versus non-PA days. In general, protein, fat, carbohydrate, and sugar consumption increased or decreased commensurately with energy intake post-PA (i.e., increased in the acute post-PA period and decreased in the remaining time in day). The relation between PA and same-day energy intake was moderated by several factors, including BMI, time of day of PA, hunger post-exercise, and the perception of having engaged in exercise. There was little evidence to suggest energy intake pre-PA, post-PA, or across entire PA days, relative to non-PA matched time periods, had a relation with percent weight change. Taken together, these findings support that engaging in PA versus not is associated with different within-person dietary patterns and those relations are moderated by biological, contextual, and psychological variables; however, there was insufficient evidence to support that observed deviations in energy intake on PA versus non-PA days are associated with weight change.