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Obesity Associated With Increased Risk of Death

But being overweight has significantly lower risk, CDC study finds (Jan. 2)

According to researchers at the Centers for Disease Control and Prevention (CDC), relative to normal weight, overall obesity (combining all grades) and higher levels of obesity were both associated with a significantly higher all-cause risk of death, while overweight was associated with significantly lower all-cause mortality.

The new findings were published in the January 2 issue of JAMA.

The researchers compiled published analyses of the body mass index (BMI) and all-cause mortality that provided hazard ratios (HRs) for standard BMI categories. For the review and meta-analysis, the researchers identified 97 studies that met inclusion criteria, which provided a combined sample size of more than 2.88 million individuals and more than 270,000 deaths.

All-cause mortality HRs for overweight (BMI of 25 to less than 30), obesity (BMI of 30 or greater), grade 1 obesity (BMI of 30 to less than 35), and grades 2 and 3 obesity (BMI of 35 or greater) were calculated relative to normal weight (BMI of 18.5 to less than 25).

The researchers found that the summary HRs indicated a 6% lower risk of death for overweight; an 18% higher risk of death for obesity (all grades); a 5% lower risk of death for grade 1 obesity; and a 29% increased risk of death for grades 2 and 3 obesity.

The investigators noted that the finding that grade 1 obesity was not associated with higher mortality suggests that most of the excess mortality in obesity may be due to elevated mortality at higher BMI levels.

The researchers added that their findings are consistent with observations of lower mortality among overweight and moderately obese patients. “Possible explanations have included earlier presentation of heavier patients, greater likelihood of receiving optimal medical treatment, cardioprotective metabolic effects of increased body fat, and benefits of higher metabolic reserves,” they wrote.

Source: JAMA; January 1, 2013.

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