AIM: To determine the acute response of appetite and appetite regulating hormones after exposure to simulated altitude. METHODS: Seven males and five females (height: 178.9 ¡ 2.3 cm; weight: 77.3 ¡ 7.2 kg; body fat: 18.4 ¡ 1.7%) participated in two, three-hour trials in a hypoxic (5000 m) and normoxic (350 m) environment. Blood samples were collected prior to and immediately following three hours of exposure for the measurement of leptin, adiponectin, and acylated ghrelin. Appetite, acute

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... in sickness, heart rate, blood oxygenation, tissue oxygenation, respiration rate, and whole body gases were also measured. RESULTS: Leptin was not different between hypoxic (5.8 ¡ 1.8 ng ml 21 ) and normoxic trials (6.2 ¡ 2.0 ng ml 21 ; p 5 0.603). Adiponectin was not different between hypoxic (9.0 ¡ 0.2 mg ml 21 ) and normoxic trials (8.4 ¡ 0.7 mg ml 21 ; p 5 0.216). Acylated ghrelin was not different between hypoxic (15.0 ¡ 3.8 pg ml 21 ) and normoxic trials (16.3 ¡ 4.6 pg ml 21 ; p 5 0.285). Appetite scores were not different between trials (p . 0.05) with the exception of fullness which was greater in the hypoxic condition (p 5 0.027). Heart rate and symptoms of acute mountain sickness were higher while blood and tissue oxygenation were lower in the hypoxic trial (p , 0.05). No differences were noted in other metabolic parameters (p . 0.05). CONCLUSION: Appetite and appetite regulating hormones are not affected by three hours of hypoxic exposure, and thus some of these negative consequences of hypoxic exposure may not be evident with short exposure times.