Fat free mass is positively associated with hunger and energy intake at extremes of obesity.

Fat mass (FM) has been shown to be negatively associated with energy intake (EI) in lean individuals but in overweight and Class I obese individuals this relationship is poorly understood. Fat free mass (FFM) is positively associated with EI in lean, overweight and Class I obese individuals. To date, the relationships between FFM, FM, hunger and EI have not been investigated in patients with a body mass index (BMI) > 35 kg/m. The aim of the present study was to examine the associations between FFM, FM, BMI, hunger and EI in individuals with severe (BMI > 35 kg/m) obesity. In total, 43 subjects (52% male) with a mean (±standard deviation) BMI of 44.5 ± 6.2 kg/m were recruited for this cross-sectional analysis. Dual energy x-ray absorptiometry and an ad libitum food buffet were used to measure body composition and EI respectively, and hunger was measured using a visual analogue scale (0-100 mm). BMI (p = 0.02; p < 0.01) and FFM (p < 0.01; p = 0.02), but not FM (p = 0.18; p = 0.71), were positively associated with both EI and pre-buffet hunger, respectively, on multivariable regression using the general linear model. These findings suggest that in extremes of obesity FFM continues to promote hunger and EI, but the inhibitory effect of FM on EI that has been observed in lean populations was not present in this cohort suffering from severe obesity.