There is a dearth of metabolic information, even for short-duration
flights, without which changes in metabolic patterns to longer flights
cannot be extrapolated. However, using scattered information, certain
changes which may be encountered can be hypothesized. Decalcification of
bone and changes in water-holding capacity of the body may be
anticipated. It is also possible that changes in proportion of fat to
lean body mass could be experienced and should be considered in
nutritional planning. Nutritional requirements depend on size,
particularly lean body mass, sex, physiological state, and individual
metabolic rates. Therefore, individuals for space flight should be
screened with these factors in mind if it is desirable to minimize food
intake in long flights. The factors which influence the total
nutritional requirements of the individual also influence his mental and
physical responses to stress.