A high fat breakfast attenuates the suppression of appetite and acylated ghrelin during exercise at simulated altitude

High-altitude exposure induces a negative energy balance by increasing resting energy expenditure and decreasing energy intake. This diminished energy intake is likely caused by altitude-induced anorexia and can have detrimental effects for those travelling to high-altitude. We aimed to investigate whether altering the macronutrient composition of breakfast could attenuate altitude-induced anorexia and augment energy intake at high-altitude. Twelve healthy men (aged 26 (8) years, body mass index 23.9 (2.7) kg·m−2) completed two, 305 min experimental trials at 4300 m simulated altitude (~ 11.7% O2). After an overnight fast, participants entered a normobaric hypoxic chamber and rested for one hour, before receiving either a high fat (HF; 60% fat, 25% carbohydrate) or an isocaloric high carbohydrate (HC; 60% carbohydrate, 25% fat) breakfast. One hour after breakfast, participants performed 60 min of treadmill walking at 50% of relative V̇O2max. An ad-libitum buffet meal was consumed 1 h 30 min after exercise. Appetite perceptions, blood samples and substrate oxidation rates were measured throughout. A significantly higher area under the curve for composite appetite score was observed during exercise in HF (40 (12) mm·h−1) compared with HC (30 (17) mm·h−1, P = 0.036). During exercise, lower insulin concentrations (P = 0.013) and elevated acylated ghrelin concentrations (P = 0.048) were observed in HF compared with HC. After exercise there was no significant difference in composite appetite score (P = 0.356), acylated ghrelin (P = 0.229) or insulin (P = 0.513) between conditions. Energy intake at the buffet did not significantly differ between conditions (P = 0.384). A HF breakfast attenuated appetite suppression during exercise at 4300 m simulated altitude, however ad-libitum energy intake did not increase.