Observations in energy and macronutrient intake during prolonged bed-rest in a head-down tilt position

Objective: to report observations in energy and macronutrient intakes, and body weight during prolonged bed-rest in a head down tilt (HDT) position. D esign: open study, each subject was his own control, and was studied during 14 days of baseline, 42 days of -6 degrees HDT bed-rest, and 12 days of re covery. Subjects: eight healthy young man were recruited, one dropped out. Methods: energy and macronutrient content of the diet were calculated from weighed amounts of food consumed and French food composition tables. Result s: body weight declined during HDT (74.0+/-3.2 to 71.8+/-3.2 kg, P < 0.001) and increased during recovery (72.7+/-3.2 kg, P < 0.001). Energy intake de creased during HDT (by 17% after 4-5 weeks) and increased during recovery b ut remained lower than during baseline (P < 0.001). During HDT fat intake, expressed by a percentage of energy, decreased (P < 0.01) while carbohydrat e increased (P = 0.04); protein intake did not change (P = 0.08). The rever se trends were observed during recovery. Conclusions: the present study rep orts a spontaneous reduction in energy and relative fat intake during prolo nged HDT bed rest. We believe that these findings have implications for the clinical setting.