The quality of weight loss was estimated during a very low calorie diet (VLCD) weight-reducing regime by determining the body composition every second week using near-infra-red interactance (NII). The study was performed on 127 overweight volunteers, aged 18-72 years, who, for eight consecutive weeks, used a VLCD to lose weight. Mean weight reduction was 12.7 kg (12.6% of initial weight). Mean body fat (BF) loss was 9.5 kg (23.8% of initial BF), which constitutes 75% of the weight loss. Mean reduction in lean body mass (LBM) was 3.2 kg (5.2% of initial LBM). We found no correlation between initial body mass index (BMI) and loss of LBM, or between initial body composition and weight loss. Weight reduction observed in this study is mainly due to reduction in body fat, and the loss of LBM is considered not to be larger than acceptable.