Components of weight loss in obese patients subjected to prolonged starvation.

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Abstract
Seven obese patients were subjected to low-calorie intake and prolonged fast. Lean tissue loss was determined from the nitrogen balance and body fat loss by the use of indirect calorimetry done intermittently throughout the study using a portable expired-air analyzer. The first week on the reduced calorie intake was characterized by a rapid rate of weight loss owing to excessive loss of salt and water and a relatively large loss of lean tissue. The lean tissue loss gradually diminished on continued fast to a constant rate between 0.9 and 1.3 g/kg per day. Fat loss was very constant throughout the fast. In seven patients the over-all mean ranged from 1.5 to 2.1 g/kg per day. Changes in body fat were calculated also from the total body water, from the difference between weight loss and lean tissue loss, and from a formula using insensible water loss. The expired-air method had the advantage that it was independent of the degree of hydration of the subject and could measure reliably the body fat changes in weekly periods.