Associations of body composition and resting metabolic rate with homeostatic and hedonic components of appetite

Background While fat-free mass (FFM), fat mass (FM), and resting metabolic rate (RMR) influence energy intake, their specific roles as homoeostatic and hedonic drivers of eating—and factors moderating these relationships—are uncertain. This study examined associations of FFM, FM, and RMR with a comprehensive set of appetite-related outcomes in adults.

Methods 130 participants (58% male; age: 25.0 ± 8.5 years; BMI: 24.0 ± 3.7 kg/m²; mean ± SD) completed assessments of RMR (indirect-calorimetry), body composition (air-displacement plethysmography), energy intake (laboratory-based), appetite-related hormones (fasted and meal-stimulated), appetite (visual analogue scales), food reward (Leeds Food Preference Questionnaire [LFPQ]), food cravings (Control of Eating Questionnaire), taste and smell perception. GLM examined associations between exposure and outcome variables, controlling for demographic and lifestyle factors. Effect modification was assessed via interaction terms and stratified analyses with median splits for continuous variables.

Results RMR was positively associated with energy intake (P < 0.001), while FFM and FM were not. The positive RMR-energy intake association was stronger in individuals who were younger, more active, smokers, and with lower BMI (P ≤ 0.020). FFM was positively associated with postprandial peptide-YY (PYY) and hunger, craving control and smell sensitivity (P ≤ 0.026). FM was positively associated with fasting PYY and leptin, and inversely associated with postprandial PYY and hunger, craving control, and taste sensitivity (P ≤ 0.047). RMR was inversely associated with fasting ghrelin (P < 0.001). No consistent associations were observed between body composition, RMR and food reward (LFPQ). Several associations were moderated by age, sex, BMI, physical activity and smoking.

Conclusions RMR is a key driver of energy intake, with sex, BMI, physical activity and smoking status moderating the relationship. Body composition (FFM and FM) is linked to distinct variations in homoeostatic and hedonic components of appetite, particularly gut hormone responses, craving control and taste perception.