Effect of a training camp in the heat on nutritional intake of well-trained endurance athletes

We investigated the effect of a training camp in the heat on energy and macronutrient intake and hunger. Twenty-two athletes completed two training periods (8 days each) of similar load. One group (HEAT, n = 14) trained successively in a temperate environment (10 ± 3°C, RH: 58 ± 11 %) and then in a hot environment (30 ± 5°C, RH: 74 ± 15%), while the other group (CON, n = 8) trained in the same temperate environment. Daily energy intake (EI), carbohydrate (CHO) and protein (PRO) intake were higher (p < 0.001) in HEAT (+23.9 ± 20.3%, +36.1 ± 24.3%, +27.5 ± 21.2%, respectively) during the heat camp compared with the temperate condition. More specifically, EI, CHO and PRO intake were greater at breakfast in HEAT (+90.1 ± 65.5%, +107.2 ± 74.3%, +69.8 ± 54.1 %, respectively). PRO intake also increased at dinner (p < 0.001) in HEAT. Mean EI and macronutrient intake during the training sessions were significantly increased (p < 0.01) in HEAT. Hunger was greater before breakfast in HEAT (p < 0.01) during the heat camp. In CON, none of the measures differed between the two training periods. These results suggest that athletes spontaneously increase their energy intake when training in the heat, with breakfast serving as the primary meal for this nutritional adjustment.