The effects o f prolonged post-absorptive state on to d y weight and b o d y fat were observed on 20 volunteers who abstained from food and water for 12 hours. Parameters studied were found to decrease at the en d o f the experimental period (28 days). Differences were observed between males an d females. The decrease in b o d y weight was significant (p < 0.01) both males and females. Changes observed in body fat were only significant (p < 0.05) for males. Energy and prote in intakes o f the volunteers were found to be sufficient, suggesting that changes had occured in the b o d y metabolism.