To compare the long-term effects of three different programs including initial 6 weeks (V)LCD diets 420 kcal/d, 530 kcal/d, 880 kcal/d) on sustained weight loss, attrition and obesity associated conventional cardiovascular risk factors. Prospective, randomized clinical 52 weeks trial. Two weeks of a booster (V)LCD period after week 26. University outpatient obesity clinic. Ninety-three middle-aged obese patients (30 men), initial mean BMI 38.7 kg/m2, age 20-65 y, from the waiting list. Weight loss pattern, attrition, reported side effects, blood pressure, blood glucose and serum lipid levels. Repeated frequent measurements up to week 26, intermittently up to final measurements at week 52. One year attrition (30-45%), sustained weight loss (8-15% of initial body weight) and changes in obesity associated risk parameters were similar in all three group. Fewer adverse events were reported in the LCD group. The results compare favorably with most previous reports of similar design. VLCD (420 kcal or 530 kcal/ d and LCD 880 kcal/d) were equally effective in long term treatment of obesity. The tendency to less side effects with LCD suggests that such preparations deserve further attention.