Other workers have reported increased adipose tissue lipoprotein lipase after a weight loss in obese subjects and have suspected that this enzyme is a primary factor of pathophysiological significance. In order to determine whether this effect was the consequence of refeeding rather than weight loss, six obese females were included in a controlled study. Adipose tissue lipoprotein lipase was measured before weight loss, at the end of 30 days on a diet of 800 kcal/day (mean weight loss 8.7%), and four times during the 8 days after the initiation of refeeding a 1500 kcal/day mixed diet to insure weight stability. Adipose tissue lipoprotein lipase decreased by 77% by the end of the weight loss, and an average 2-fold increase (24.2 +/- 2.7 mean +/- sem versus/11.1 +/- 2.3 mU/10(6) cells, p less than 0.01) was shown as early as 2 days after refeeding. Peak values after refeeding did not surpass predieting values. Changes during restriction and peak postrefeeding values were both positively correlated to baseline values. It can be concluded that the previously shown increase in lipoprotein lipase during weight stability after a weight loss is likely to be a secondary effect of partial refeeding; the individual sensitivity of adipose tissue lipoprotein lipase to nutritional induction could be of critical importance.