Very low calorie diets (VLCD) have many advantages, as they are inexpensive, safe and easy to comply with, and give rapid and encouraging weight loss. On the other hand, many patients complain of hunger and constipation. We have shown that these drawbacks can be reduced by the supplementation of 30 g of dietary fibre to VLCD. By the use of a VLCD which provides approximately 60 g of protein for women and approximately 70 g for men, the dietary regimen is safe and no excessive loss of lean body mass seems to occur during VLCD in obese patients. However, the changes in body composition that may occur after cycles of weight loss and regain have not been clarified. After weight cycles with weight losses obtained by conventional diets, obese women have lower lean body mass than obese non-dieting controls. Hence, more information about the changes in body composition during dieting on conventional diets and VLCD are needed.