Acute effect of environmental temperature during exercise on subsequent energy intake in active men

Background: The performance of exercise while immersed in cold water has been shown to influence energy intake in the subsequent meal. However, the effect of ambient temperature during land-based exercise is not known. Objectives: Our aims were to investigate the effect of exercise performed in the heat on energy intake in the subsequent meal and to determine concentrations of circulating appetite-related hormones. Design: In a randomized, counterbalanced design, 11 active male participants completed 3 experimental trials in a fasted state: exercise in the heat (36 degrees C), exercise in a neutral temperature (25 degrees C), and a resting control (25 degrees C). The exercise trials consisted of treadmill running for 40 min at 70% (V) over dotO(2peak). After each trial, participants were presented with a buffet-type breakfast of precisely known quantity and nutrient composition, which they could consume ad libitum. Results: Energy intake was greater after exercise in the neutral temperature compared with the control (P = 0.021) but was similar between exercise in the heat and the control and between the 2 exercise trials. When accounting for the excess energy expended during exercise, relative energy intake during exercise in the heat was lower than the control (P = 0.002) but was similar between exercise in the neutral temperature and the control and between exercise in the heat and in the neutral temperature. The lower relative energy intake after exercise in the heat was associated with an elevated tympanic temperature and circulating concentrations of peptide YY (P < 0.05). Conclusion: Exercise in a neutral environmental temperature is associated with higher energy intake in the subsequent meal compared with a control, whereas exercise in the heat is not. Am J Clin Nutr 2009; 90: 1215-21.