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In 1991, a total of 8 people were sealed for 2 years inside a man-made “Biosphere” consisting of a 3-acre ecologically closed habitat. This crew of 4 men and 4 women voluntarily entered the habitat to learn about the interactions between humans and key ecological systems. However, these scientists serendipitously experienced a hardship that has actually taught the world a great deal more about basic human physiology than ever expected. In the first growing season after entering the Biosphere, an unplanned crop failure resulted in a relative famine in their ecological bubble. This crop failure resulted in a severe calorie imbalance, with an estimated 1784 daily calories per person for the first 6 months instead of the 2000-calorie allowance that was available after the first growing season. In addition, the physical labor needed to survive within the Biosphere (devoid of most modern conveniences) was enormous. The men and women lost a mean of 21% and 14% of their weight, respectively. The physiological changes measured in response to this caloric deficit were judged as medically favorable. Major reductions in blood pressure and levels of insulin, blood glucose, hemoglobin A1c, uric acid, low-density lipoprotein cholesterol, and triglycerides were found. Their bodies burned fat for energy, and all the while, preserved their levels of albumin, transferrin, iron, and other important micronutrients.1
Inge TH, Siegel RM, Xanthakos SA. Weight Loss MaintenanceA Hard Nut to Crack. JAMA Pediatr. 2014;168(9):796-797. doi:10.1001/jamapediatrics.2014.672