Does feeding regime affect physiologic and thermal responses during exposure to 8, 20, and 27 degrees C?

When the loss of body heat is accelerated by exposure to low environmental temperatures, additional substrates must be oxidized to provide energy to sustain temperature homeostasis. Therefore, the present investigation examined the relation between feeding regime [pre-experimental carbohydrate feeding (FED) vs a fast (FAST)], during 120 min of exposure to 8, 20, and 27 degrees C in well-nourished men. The following were examined: tissue insulation (I; degrees C.m2:W-1), rectal temperature (Tre; degrees C), and oxygen consumption (VO2; ml,kg-1.min-1). VO2, Tre, and I revealed no significant differences between treatments (FED vs FAST) at any temperature. At 27 degrees C, I was less (P < 0.05) than at 20 and 8 degrees C, and decreased (P < 0.05) as exposure time increased. At 8 degrees C, VO2 was higher (P < 0.5) than at 20 or 27 degrees C, and VO2 increased as time increased (P < 0.05). Tre decreased (P < 0.05) as time increased for all conditions. Respiratory exchange ration (R) differed (P < 0.05) between treatments (FED vs FAST), temperature (8 vs 20 degrees C), and across time. Values for R suggests that carbohydrate accounted for 56% and 33% of caloric utilization during the FED vs FAST conditions, respectively. At 8 vs 20 degrees C, R represented 54% vs 30% of carbohydrate utilization. Across time, R demonstrated that in both conditions (FED vs FAST) there was a decreased reliance on carbohydrate utilization for energy provision.(ABSTRACT TRUNCATED AT 250 WORDS)