The thermogenic effect of a carbohydrate feeding during exposure to 8, 12 and 27 degrees C

The increased metabolic heat production in humans exposed to cold stress results from an increased oxidation of both carbohydrate and fat to provide energy to sustain temperature homeostasis. Research suggests that dietary manipulations may enhance metabolic heat production, thereby delaying hypothermia. Therefore, the present investigation examined the thermogenic effect of a sequential timed feeding regime of either a carbohydrate (CHO) or a placebo beverage (PL) before and again midway through 120 min of exposure to 8, 12 and 27 degrees C in well-nourished men. The following were examined: tissue insulation (I), rectal temperature (Tre), mean skin temperature (Tsk), metabolism (M), time-weighted heat production and respiratory exchange ratio (R). Tre, delta Tre, Tsk, M, delta M, I and time-weighted heat production revealed no significant differences between treatment (PL vs CHO) at any temperature (8, 12 and 27 degrees C). However, Tre decreased (P < 0.05) as time increased at 8, 12 and 27 degrees C while M increased (P < 0.05) and I decreased (P < 0.05) at 8 and 12 degrees C. At 8 and 27 degrees C, R differed (P < 0.05) between the PL and CHO treatments. In addition, at 8 and 12 degrees C, R increased (P < 0.05) across time reflecting the feeding. From these data it appears that while substrate utilization differed between dietary treatment (8 and 27 degrees C) and across time, this feeding regime did not differentially affect M, Tre, Tsk and I during 120 min of exposure to 8, 12 and 27 degrees C.