Many epidemiological and clinical studies in recent years have confirmed a positive correlation between the serum urate concentration and body weight. The aim of the present study was to determine whether weight reduction in obese people had any effect on the urate metabolism. Twenty-two massively o bese subjects, eight men (183 ± 30% of ideal body weight) and fourteen women (170 ± 21% of ideal body weight), were hospitalized and treated with low-calorie diets (800 - 1,000 kcal) for intensive weight reduction, and an exercise therapy (walking and bicycle ergometer) was added to this regime afterwards. We examined serum levels of uric acid, creatinine, lipids and lipoproteins as well as urinary urate and creatinine excretions, and then calculated urate clearance (CUA) to creatinine clearance (CCR) ratio. Urinary urate excretions were not increased, but rather reduced. CUA/CCR ratios (%) were significantly lower in both sexes (3.3 ± 1.2% in male and 5.1 ± 3.3% in female, respectively) than control subjects. These data suggest that hyperuricemia in massively obese people is mainly due to an impaired renal clearance ratio of uric acid rather than overproduction. During weight reduction by a low-calorie diet, serum levels of cholesterol and triglyceride fell gradually except for HDL-cholesterol. Serum urate levels were also reduced during weight reduction, while CUA/CCR ratios gradually rose up to almost normal levels. This increase of CUA/CCR ratio was also maintained after the exercise therapy. The mechanism of the imp r ovement in urate metabolism during weight reduction is yet unclear, but a reduced intake of total calorie or purine nucleotides might be a possible mechanism.
