Short-term effects of growth hormone on bone metabolism and soft tissue collagen metabolism during weight loss in obese subjects on a very low calorie diet were investigated in a double-blind, placebo-controlled design. Twenty healthy, obese women (body mass index between 33 and 45 kg/m2) aged 21-48 yr were followed for 8 wk: half received growth hormone. A 740-kcal diet was administered the first 4 wk, followed by a 1200-kcal diet. Lumbar spine body mineral context (BMC), total-body fat mass, total-body lean body mass, total-body BMC, and total-body bone area were measured by dual-energy X-ray absorptiometry along with biochemical markers of bone turnover. The body weight decreased by 5.5% and fat mass by 11.4%. There were no changes in biochemical bone markers in the placebo group despite a marked decrease in BMC (3.1%). Projected total bone area decreased proportional to BMC (r2 = 0.89) during the weight loss. Growth hormone treatment did not modulate the decrease in lean body mass, body weight, fat mass, or BMC, but increased bone turnover markers. Growth hormone did not change the results concerning BMC, projected bone area, BMD, lean body mass, or fat mass. Because 89% of the observed change in BMC could be explained by alterations in projected bone area without changes in biochemical bone markers, it is concluded that a large part of the observed decrease in BMC during weight loss may be caused by scanner artifact.