Experiments were performed to establish the activity and performance of man kept on a low-calorie (1800) diet and exposed to some space flight effects. The diet consisted of canned foods with an optimal proportion of basic nutrients and amino acids. Three series of experiments were carried out on 18 healthy male subjects. Each series involved pre- and post-test examinations and 15-day tests. The first series dealt with the effect of low-calorie diets as such; the second one covered the effect of low-calorie diets combined with bed rest; and the third series revealed the above effect aggravated by exposing test subjects to bed rest and acceleration. In the course of the experiments, the state of the central nervous and cardiovascular systems, the function of external respiration, the digestive function, the kinesthetic apparatus, metabolic processes and immunological resistance of the body were studied. In addition, test subjects underwent thorough clinical examinations. The paper presents results of the experiments.