Ten obese non-insulin-dependent diabetics (six men, four women) with secondary drug failure were treated with a hypocaloric diet only (2100-3350 kJ/d) for 3 mo to assess the effects of weight reduction on metabolic control, energy production rate, and cardiovascular risk factors. During the 3 mo of follow-up the mean body weight decreased from 101.0 +/- 7.2 (means +/- SEM) to 87.2 +/- 5.5 kg (p less than 0.001). Basal energy production rate (kJ/min) decreased by 8.5%. Fasting blood glucose declined from 12.3 +/- 0.4 to 10.5 +/- 0.7 mmol/L (p less than 0.05) but mean diurnal glucose and glycosylated hemoglobin A1c did not change significantly. Serum total cholesterol was decreased at 2 wk but at 3 mo it did not differ significantly from the baseline value. A marked reduction was observed in serum triglycerides after 3 mo (4.57 +/- 1.0 vs 2.18 +/- 0.26 mmol/L, p = 0.012). The high-density lipoprotein (HDL) cholesterol increased after weight reduction (0.96 +/- 0.06 vs 1.11 +/- 0.05 mmol/L, p = 0.009). A significant decline was found in both systolic (152 +/- 6 vs 133 +/- 3 mm Hg, p = 0.004) and diastolic blood pressure (92 +/- 3 vs 81 +/- 3 mm Hg, p = 0.007). There was no evidence of linoleic acid deficiency after this diet.