This study investigated the effects of hypoxia on appetite regulation in women while strictly controlling for diet, physical activity, menstrual cycle, and environmental conditions. In young women, 4 days of altitude exposure (3,500 m) decreases body weight and circulating acylated ghrelin levels while preserving leptin concentrations. In line with the hormonal changes, altitude exposure induces alterations in appetite sensation, consisting of a decreased feeling of hunger and prospective food intake and an increased feeling of fullness and satiety.