The fatty acid compositions of abdominal and gluteal subcutaneous adipose tissues of eight obese subjects were measured after an initial 5-10-wk period of weight maintenance on a liquid-formula diet (40% of calories as corn oil, 45% as carbohydrate, and 15% as protein), after a 10% increase in weight (11-20 kg) on a solid-food diet of each subject's choice (n = 5) or after a 20% decrease in weight (26-37 kg) on 800 kcal/d of the same corn-oil-formula diet (n = 5). After weight gain or weight loss, all subjects maintained their new weights for 2-10 wk on the same corn-oil-formula diet. As hypothesized, there were minimal changes in the concentrations of 41 fatty acids identified in both abdominal and gluteal tissues after all dietary phases, and small site-specific differences in the levels of saturated and monounsaturated fatty acids were not altered. The largest change was a 15% decrease (P less than 0.05) in 18:3n-3 in both abdominal and gluteal tissues during weight loss, despite higher levels in the diet than in the baseline adipose tissue. This decrease occurred without coexisting decreases in 22:5n-3 and 22:6n-3, two elongase-desaturase products of 18:3n-3 that were not detectable in the diet.