According to a study, after a week of high-altitude living, twenty men had slimmed down  The men, middle-aged residents of low-altitude areas, had been taken to a research station at 2, 650 meters (8, 694 feet) above sea level  They had unrestricted access to food and were forbidden vigorous exercise, yet they lost an average of 1  5 kilograms (3  3 pounds) during their one-week stay
Clearly, the lower availability of oxygen at higher altitudes, or hypobaric hypoxia, can be said to have caused the weight loss, since
a decrease in oxygen intake has been shown to depress appetite