The effects of a 3 week weight reduction regimen on lipids and lipoproteins, in particular high density lipoprotein (HDL)-subfractions in 61 grossly obese children and adolescents (37 females and 26 males) aged 11-15 years were studied. Dietary treatment resulted in a significant weight reduction of initial body weight of 9.6 +/- 2.1%, a highly significant decrease in cholesterol, low density lipoprotein cholesterol (LDL-C) and HDL-C (P less than 0.001), as well as a significant reduction in triglycerides, HDL3 and Apolipoprotein B concentrations (P less than 0.01). HDL2 concentrations remained almost constant. It is concluded that HDL reduction during a weight reducing regimen in adolescents does not result in a decrease of the antiatherogenic HDL2 subfraction.