Obesity Abstracts

Background: Previous research suggests that resting metabolic rate (RMR) is a determinant of self-selected meal size and 24-hour energy intake (EI) under laboratory and free-living conditions. However, whether the accumulation of adipose tissue weakens the coupling between RMR and EI has yet to be examined. The aim of this study was to examine if body fat percentage moderated the association between RMR and 24-hour EI in women across a range of body mass index (BMI).

Methods: 74 women (age=33.4±10.2 y) were recruited and stratified using two a priori categories (lean-n=27, BMI=18.5–24.9 kg/m²; overweight/obesity-n=47, BMI=25.0–34.9 kg/m²). Body composition (air displacement plethysmography), RMR (indirect calorimetry) and 7-day free-living 24-hour EI (online food diary – myfood24.org) were assessed, and moderation analysis was conducted (PROCESS macro version 3.1) to examine the influence of body fat percentage on the association between RMR and EI. The EI/RMR ratio was calculated to assess whether reporting plausibility affected any observed associations.

Results: A positive association was observed between RMR and 24-hour EI (r=0.395; P<0.001), and this association was moderated by body fat percentage (β=−2.310; P=0.019). The conditional effect of body fat percentage on RMR was statistically significant at the lowest (−1SD=25.6%; P=0.0001) and medium (mean=36.7%; P=0.0003) levels of the moderator, but not at the highest (+1SD=44.4%; P=0.145), suggesting that the association between RMR and 24-hour EI weakens with increased adiposity. There was no association between the EI/RMR ratio and body fat percentage (r=0.083; P=0.482), suggesting that the moderation effect was not influenced by reporting plausibility. Pearson correlation coefficient indicated that the association between RMR and EI was stronger in lean (body fat percentage=26.4±5.7%; r=0.554, P=0.003) than in women with overweight and obesity (body fat percentage=41.1±5.6%; r=0.310, P=0.034).

Conclusions: Consistent with previous research, RMR was associated with free-living 24-hour EI, but these data further suggest that this association might be moderated by body fat percentage. As the association between RMR and EI was stronger in leaner individuals, the accumulation of body fat may be detrimental to an individual’s ability to accurately match EI to energy requirements.

Keywords: Resting metabolic rate, energy intake, body fat percentage

Disclosures: None.