Looking for a new weight loss plan? Try living on top of a mountain. Mountain air contains less oxygen than air at lower altitudes, so breathing it causes the heart to beat faster and the body to burn more energy. A handful of studies have found that athletes training at high altitudes tend to lose weight. Doctor Florian Lippl of the University Hospital Of Ludwig-Maximilians-university Munich wondered how the mountain air would affect overweight individuals if they weren't doing any more physical activity than usual. Lippl and his colleagues invited 20 overweight men to an environmental research station about 300 meters below the summit of Zugspitze, a mountain around 2,970 meters near the Austrian border. They were allowed to eat as much as they liked. The men also gave blood so that researchers could test for hormones linked to appetite and fatness. At the end of the week, the men, whose mean weight starting out was 105kg, had lost on average about l.5kg. The men's blood pressure also dropped, which the researchers believed was due to weight lost. Exactly what caused the weight loss is uncertain. Loss of appetite is common at higher altitudes, and indeed the men ate significantly less than usual--about 700 calories fewer per day. Lippl also notes that because their consumption was being recorded, they may have been more self-conscious about what they ate. Regardless, eating less accounts for just l kg of the l.5 kg lost, says Lippl. He thinks the increased metabolic   rate, which was measured, also contributed to weight loss but cannot separate the different effects with the given data. Appetite loss at high altitudes could certainly be key, notes Damian Bailey, a physiologist at the University of Glamorgan, UK, who recently lost 11 kg during a 3-month expedition to the Andes in Chile. Unfortunately, for the average person there is no treatment that can resemble living at high altitude, says Lippl. The only alternative is hypobaric chamber, which exposes subjects to low oxygen and isn't practical as a treatment. He says, half- jokingly, "If fat people plan their holidays, they might not go to the sea, but maybe to the mountain." Hormones are tested in the research because they can affect   _  .
one's bodyweight one's blood pressure one's way of living one's metabolic rate