Purpose: Hypoxia has been shown to reduce energy intake and lead to weight loss, but the underlying mechanisms are unclear. The aim was therefore to assess changes in eating after rapid ascent to 4,559m and to investigate to what extent hypoxia, acute mountain sickness (AMS), food preferences and satiation hormones influence eating behavior. Methods: Participants (n=23) were studied at near sea level (Zurich (ZH), 446m) and on two days after rapid ascent to Capanna Margherita (MG) at 4,559m (MG2 and MG4). Changes in appetite, food preferences and energy intake in an ad libitum meal were assessed. Plasma concentrations of cholecystokinin, peptide tyrosine-tyrosine, gastrin, glucagon and amylin were measured. Peripheral oxygen saturation (SpO2) was monitored, and AMS assessed using the Lake Louis score. Results: Energy intake from the ad libitum meal was reduced on MG2 compared to ZH (643±308 vs. 952±458kcal, p=0.001), but was similar to ZH on MG4 (890±298kcal). Energy intake on all test days was correlated with hunger/satiety scores prior to the meal and AMS scores on MG2 but not with SpO2 on any of the 3days. Liking for high-fat foods before a meal predicted subsequent energy intake on all days. None of the satiation hormones showed significant differences between the 3days. Conclusion: Reduced energy intake after rapid ascent to high altitude is associated with AMS severity. This effect was not directly associated with hypoxia or changes in gastrointestinal hormones. Other peripheral and central factors appear to reduce food intake at high altitud
