Thirty-three obese women were admitted as inpatients to a metabolic ward and had an average intake of 3.35 MJ (800 kcal) daily for three weeks. Fat biopsies were taken at three subcutaneous sites and average fat cell mass (CM) and apparent fat cell number (FCN) were calculated. There was no significant correlation between adipose tissue cellularity (CM or FCN) and total weight loss or resting metabolic rate, provided due allowances were made for the severity of obesity in each case. Neither was there any significant correlation between short-term weight loss and the age of onset of obesity. Resting metabolic rate, and not adipose tissue cellularity or age of onset of obesity, is a better indicator of short-term weight loss under controlled inpatient conditions.