Only a Little Extra Weight Increases Death Risk

ROCKVILLE, Md., Aug. 22 -- Even carrying a few extra pounds in patients who are not frankly obese is enough to increase the risk of death, according to two large studies.

A prospective study of 527,265 American men and women, who were 50 to 71 years old when the study started, found that being overweight at midlife (age 50) increased the risk of death by 10 to 30%.

And an analysis of more than 1.2 million Koreans, ages 30 to 95, found that the risk of death from any cause was lowest for a normal weight, and increased for those underweight, overweight, or obese.

"Our findings suggest that adiposity, including overweight, is associated with an increased risk of death," reported Kenneth Adams, Ph.D., of the National Cancer Institute here.

The Korean researchers, led by Sun Ha Jee, Ph.D., of Yonsei University in Seoul, found that underweight people tended to die of respiratory diseases, while overweight and obese people had increased rates of atherosclerotic cardiovascular deaths and cancer deaths.

Both studies were published in the Aug. 24 issue of the New England Journal of Medicine.

The American study looked risk of death from any cause among people in the National Institutes of Health-AARP cohort, which began enrolling volunteers in 1995, and related the risks to the body mass index (BMI), defined as weight in kilograms divided by the square of the height in meters.

A person with a BMI of 30 or more is regarded as obese, while BMI between 25 and 29.9 is regarded as overweight. A normal BMI is defined as between 18.5 and 24.9.

Complicating the issue is smoking, which simultaneously reduces BMI and increases the risk of death, but the cohort was large enough, Dr. Adams and colleagues said, that it was possible to tease out the effects of tobacco.

Compared with participants who had a BMI of 23.5 to 24.9 at age 50:

• Overall, the risk of death among participants who were overweight at 50 years was 10% to 30% higher.
• The risk was even higher in overweight men (30% to 50%) and women (20% to 40%) who had never smoked.
• The risk among obese subjects was two to at least three times higher.
• The risk of death among underweight participants - BMI below 18.5 -- was 50% higher.

The Korean study looked at 12-year follow-up data from a prospective cohort of 1,213,829 people who had undergone physical exams through the country's National Health Insurance Corporation.

The mean BMI among the participants was 23.5 and a majority of participants had a BMI below 25, according to Dr. Jee and colleagues.

Compared with all men with a BMI of 23.0 to 24.9, the study found:

• Men who had never smoked and who had a BMI of less than 18.5 had a hazard ratio for death from any cause of 1.29 (with a 95% confidence interval from 1.15 to 1.44).
• Those with a BMI of 25.0 to 29.9 had a hazard ratio of 1.04 (with a 95% confidence interval from 0.98 to 1.10).
• And those with a BMI of 30 or more had a hazard ratio of 1.71 (with 95% confidence interval from 1.44 to 2.03).

For women who had never smoked, the hazard ratios were similar or slightly lower in each category. Dr. Jee and colleagues found that smokers of both sexes and all BMI levels had an increased risk of death, compared with non-smokers with a BMI of 23.0 to 24.9.

The findings are a "sobering reminder" that increased adiposity is a world-wide problem that is bringing with it a host of chronic diseases, commented Tim Byers, M.D., of the University of Colorado School of Medicine in Denver.

In particular, Dr. Byers noted in an accompanying Perspective article, the Korean study found increased risk of all-cause mortality even at levels of adiposity that would be regarded as modest in North America.

And, as the population ages, the overweight proportion is also likely to increase, Dr. Byers noted, unless something is done to curb the trend. "Fortunately, evidence points to a substantial health benefit from even small changes in weight trajectory," Dr. Byers said.

For clinicians, the message of the two studies, he concluded, is that even small steps toward curbing the age-related weight gain are likely to prove beneficial.