Thermic effect of meal and fat mass in lean and obese men

Abstract

This study was designed to investigate the eventual impact of fat mass (FM) on the thermic effect of a meal (TEM) in obesity. Eight lean (BMI : 18.3 – 23.9) and eleven obese (BMI : 27.3 – 32.7) men with similar fat free mass (FFM), but very different fat mass participated in the study. Body composition was assessed by bioelectrical impedance analysis (BIA) at 5 kHz and 1 MHz. Metabolic rates were measured by indirect calorimetry before and after a 4055 kJ (969 kcal) mixed meal. Resting metabolic rates (RMR) were not significantly different between the two groups. The RMR was significantly correlated with FFM (Kendall rank correlation coefficient τ = 0.6, p ≤ 0.0001) and FM (τ = 0.47, p < 0.002). As expected, TEM, expressed in absolute values (303.6 vs 515.3 kJ, p ≤ 0.002) or as a percentage of the test meal energy load (7.5% vs 12.8%, p ≤ 0.002), was significantly lower in the obese than in lean men, respectively. At FFM kept constant, TEM was negatively correlated with absolute FM (τ = −0.34, p ≤ 0.02) and percent FM (τ = −0.35, p ≤ 0.02). FM, whatever the way to express it, was negatively correlated with TEM in sedentary young adult lean and obese men.