Part of the crew dining room, serving counter from kitchen and stairway up to an entertainment area | Wikimedia Commons Eight people entered Biosphere 2 in Arizona in September 1991, where they expected to live inside a sealed ecological system for two years. Instead, crop yields were lower than planned and the crew spent much of the mission on a nutrient-dense diet that provided roughly 1,750 to 2,100 calories a day.The crew had completed the two-year confinement when the first mission ended in September 1993. A later medical study found that their average body weight had fallen by 17%, while insulin levels declined 42% and cholesterol fell 30%. The researchers reported that the crew members nevertheless remained in good health and maintained high levels of physical and mental activity during the mission. The numbers came from a very small group: four women and four men. Seven crew members were between 27 and 42 years old, while one was 67.
Part of the crew dining room, serving counter from kitchen and stairway up to an entertainment area | Wikimedia Commons
The food system produced less than expectedThe first Biosphere 2 mission ran from September 1991 to September 1993, and the facility had been designed to recycle air, water and organic material while producing much of the crew’s food inside the enclosure. A study of the agricultural system found that the roughly 2,000-square-meter cropping area supplied about 81% of the crew’s nutritional needs over the two-year mission. The diet was primarily vegetarian, with vegetables, fruits and grains supplemented by milk, meat and eggs from animals that were kept inside the facility.Researchers studying the agricultural system reported problems with broad mites and root-knot nematodes, which forced the crew to change crops and adapt food production during the mission. The diet averaged about 2,200 calories per person per day across the full two years, although intake was considerably lower during the period of food restriction. The lower intake became a persistent part of daily life, and agriculture, food preparation and animal care also consumed a large share of the crew’s working time.The experiment was intended to test whether humans could maintain themselves inside a closed ecological system, and the food shortages became one of the practical problems that the crew had to manage alongside farming and waste recycling.Hunger became part of daily lifeJane Poynter, one of the original crew members, later described the experience in an essay published by the University of Arizona Press. She wrote that the residents experienced hunger throughout the two years and that meals were consistently consumed completely. Poynter described the group as effectively becoming subsistence farmers inside a highly engineered facility, who grew much of what they ate and had to work around the limited enclosed agricultural system.Because the food supply remained nutritionally adequate while calories were restricted, the crew became a small group in which researchers could observe physiological changes associated with sustained lower energy intake. The later medical study found that the crew consumed 1,750 to 2,100 calories per day for seven-eighths of the confinement, rather than for the full two years.Weight fell fastest at the beginningThe 2002 study reported an average loss of 17% weight, with a variation of plus or minus 5%. The researchers tracked 50 variables for each crew member and compared measurements taken before entry, during confinement and after the crew returned to an unrestricted diet.The study also reported a 42% reduction in insulin and a 30% reduction in cholesterol. Blood sugar declined 21%, while systolic and diastolic blood pressure fell by 25% and 22%, respectively. These measurements were observations from eight people living under an unusual combination of calorie restriction, physical work and confinement, and it is important to note that the study did not establish that calorie restriction alone produced every change.The researchers did, however, conclude that the physiological and biochemical changes resembled those previously observed in animals subjected to calorie restriction. The study reported that despite the weight loss and reduced calorie intake, all eight members remained in excellent health and sustained high levels of physical and mental activity.
Residential area inside Biosphere 2 | Wikimedia Commons
The diet became a research subjectThe original purpose of the Biosphere 2 mission was not to conduct a controlled human calorie-restriction trial, since the food limitation emerged from the difficulties of producing enough food inside the sealed environment. The eight participants were not randomly assigned to a calorie-restricted diet, and there was no comparable control group living under the same conditions.Researchers instead used measurements taken before, during and after the confinement to track changes in the same individuals. Blood samples were collected repeatedly during the mission and again after the crew returned to an unrestricted diet.The follow-up period lasted another 30 months, and that allowed the researchers to observe what happened after the crew left the sealed environment and resumed eating without the same restrictions. The Biosphere 2 mission ended in September 1993, but the medical data collected from those two years continued to be analyzed afterward. The 2002 paper ultimately treated the crew’s experience as evidence that healthy, nonobese people could undergo substantial physiological changes during prolonged intake restriction while maintaining adequate nutrition.