Anton A. van Steenhoven, † and Wouter D. van Marken Lichtenbelt* Abstract

production and body temperature during cooling and rewarming in overweight and lean men. Obesity. 2006;14: 1914–1920. Objective: To compare overweight and lean subjects with respect to thermogenesis and physiological insulation in response to mild cold and rewarming. Research Methods and Procedures: Ten overweight men (mean BMI, 29.2! 2.8 kg/m2) and 10 lean men (mean BMI, 21.1! 2.0 kg/m2) were exposed to cold air for 1 hour, followed by 1 hour of rewarming. Body composition was determined by hydrodensitometry and deuterium dilution. Heat production and body temperatures were measured con-tinuously by indirect calorimetry and thermistors, respec-tively. Muscle activity was recorded using electromyogra-phy. Results: In both groups, heat production increased signifi-cantly during cooling (lean, p " 0.004; overweight, p " 0.006). The increase was larger in the lean group compared with the overweight group (p " 0.04). During rewarming, heat production returned to baseline in the overweight group and stayed higher compared with baseline in the lean group (p " 0.003). The difference in heat production between rewarming and baseline was larger in the lean (p " 0.01) than in the overweight subjects. Weighted body temperature of both groups decreased during cold exposure (lean, p " 0.002; overweight, p # 0.001) and did not return to baseline during rewarming. Discussion: Overweight subjects showed a blunted mild cold-induced thermogenesis. The insulative cold response was not different among the groups. The energy-efficient response of the overweight subjects can have consequences for energy balance in the long term. The results support the concept of a dynamic heat regulation model instead of temperature regulation around a fixed set point. Key words: cold, energy balance, individual variation, body composition, temperature distributio