In a 105-day experiment simulating crew life in a space exploration vehicle, shifts in the nutritional status were assessed in 6 test subjects differing in the body mass index, basal metabolism, attitude to the diet, physical exercise and workload. Results of the investigation showed that because of the hard physical work the nutritional status of test subjects was described by more intensive basal metabolism, elevated metabolism of carbohydrates and lipids, and their increased mobilization from depots. Food ration, though it was sufficient to sustain health and fairly high performance, failed to meet fully individual taste preferences and energy needs for physical activities. The heavy workloads required mobilization of lipids from adipose depots, and a decrease of the hepatic detoxification and metabolic capacities. Self-limitation of eating protein-rich desserts led to a relative deficiency of protein intake. These faults of the diet were the reason why 4 out of 6 test subjects reduced their basal metabolism and lost body mass. Recovery of metabolism and slowdown of the body mass loss were achieved by supplementing meals with available protein-containing products.