Factors influencing body composition during very-low-calorie diets.

Apparent body composition changes with weight loss on very-low-calorie diet (VLCD) can depend on the method of fat-free mass estimation. In this report the implications of differences in measurement by direct versus indirect methods are examined. The nitrogen sparing and protein economy associated with ketosis is relevant and results of clinical trials with diets of varying composition are presented. The analytical findings of a multicenter, multimethod long-term VLCD study illustrate protein and metabolic conservation during VLCD. Protein losses, by total body nitrogen, over 10 wk dieting, independent of body mass index, were 4.75% of weight lost, as conservatively expected from obesity tissue reduction with no degradation of total energy expenditure. The implications of utilization of glycogen (water and potassium release) in interpretation of diet success and of body compositional change is evaluated. Evidence is presented that ultimate compositional changes with weight change may be individually specific and that body composition may be predicted from weight considerations alone.