text: The magnitude and composition of the starvation response (i.e. metabolic adaptation) was estimated in a study of 8 individuals living in isolation in Biosphere 2 for two years. During their isolation, they gradually lost an average of 15% (range: 9–24%) of their body weight due to harsh conditions. On emerging from isolation, the eight isolated individuals were compared with a 152-person control group that initially had similar physical characteristics. On average, the starvation response of the individuals after isolation was a  reduction in daily total energy expenditure.  of the starvation response was explained by a reduction in fat-free mass and fat mass.  An additional  was explained by a reduction in fidgeting. The remaining  was statistically insignificant.