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Japanese people with hyperuricemia saw some reductions in urate levels when they lost weight, with greater losses tied to greater decreases in serum urate, researchers said.

Among people with urate levels at 7.0 mg/dL or higher, one kilogram of lost weight correlated with a mean decrease in serum urate level of 0.052 mg/dL, according to Sho Fukui, MD, MPH, of Brigham and Women's Hospital in Boston and St. Luke's International Hospital in Tokyo, and colleagues.

When weight loss was expressed categorically, the group , it was associated with urate reductions as follows:

• "Small" losses (1.0-4.9 kg): -0.10 mg/dL (95% CI -0.10 to -0.09)
• "Moderate" losses (5.0-9.9 kg): -0.34 mg/dL (95% CI -0.36 to -0.32)
• "Large" losses (≥10.0 kg): -0.64 mg/dL (95% CI -0.70 to -0.58)

And, when the data were analyzed to yield a number needed to treat (NNT) -- i.e., how many people would need to lose a given amount of weight to achieve serum urate levels less than 6 mg/dL -- Fukui and colleagues came up with these NNT values:

• Small weight loss: 61.1
• Moderate loss: 8.5
• Large loss: 3.6

Fukui's group acknowledged that weight losses of less than 5 kg didn't make a clinically significant difference in serum urate. But losing greater amounts could, by itself, be a means to bring urate under control for at least some patients.

"Moderate to large weight reduction would be a reasonable treatment option to control [serum urate] levels in overweight patients with gout," they concluded.

Motivation for the study came from the long-recognized association between obesity, serum urate, and gout. Weight loss is commonly recommended for gout patients, and studies of people undergoing bariatric surgery have shown substantial urate reductions among the many benefits. Associations between lesser weight reductions and urate, however, haven't been clearly established.

To get a better handle on this issue, Fukui and colleagues drew on a database of annual examination results for people seen at St. Luke's International Hospital's preventive medicine center -- a total of 58,630 patients seen at least twice from 2012 to 2022. (As the authors explained, all full-time employed people in Japan are required to undergo such exams, making this sample fairly representative of the general able-bodied adult population in Tokyo.)

Most of the patients in the sample were relatively healthy. Median age was 46, and just over half were women. Median body mass index was 22.0, with just 16.5% classified as overweight and 2.9% as obese. The median number of exams was five, and the median follow-up was 5.3 years.

Median serum urate levels stood at 5.3 mg/dL. Still, more than 25,000 individuals had urate levels of 7.0 mg/dL or higher at some point. Among this group, 7,456 had small weight losses following a urate reading this high, 1,383 had moderate losses, and 278 had large losses. The distribution was similar when analyzed per visit rather than per patient.

Another way to look at the relationship between weight loss categories and achievement of serum urate <6.0 mg/dL was via relative risk. Fukui and colleagues calculated the following, reflecting adjustment for covariates and relative to people with only minimal weight change:

• Small losses: 1.25 (95% CI 1.15-1.37)
• Moderate losses: 2.82 (95% CI 2.43-3.27)
• Large losses: 5.27 (95% CI 4.15-6.70)

The researchers also noted that changes in alcohol intake and diet -- other factors tied to gout and hyperuricemia risk -- were not nearly as strongly associated with changes in urate levels as was weight loss.

Limitations to the study included a lack of information on some other factors that may influence urate levels, notably medication use; people with major comorbidities were also excluded. Moreover, reasons for weight loss were not examined. Finally, the findings in Japanese people might not be readily generalizable to the U.S. and other Western countries.

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