Last Updated: 2003-01-07 17:00:53 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Obesity is a well-known risk factor for heart disease, diabetes and other chronic diseases that can cause premature death. Now, two national studies reveal that obesity can, on average, cut more than a decade from a person's life. For black men it can shorten life by up to 20 years.

The findings support the notion that excess body weight is more than a cosmetic problem, and may spur individuals, doctors and public health officials to redouble efforts to keep weight in check.

"Excess weight has not received the same attention from clinicians and policymakers as have other threats to health such as tobacco use, hypertension, or (high cholesterol)," Drs. JoAnn E. Manson and Shari S. Bassuk from Brigham and Women's Hospital in Boston, Massachusetts, write in an accompanying editorial. "It is not surprising that obesity rates continue to climb."

According to both studies, obesity is particularly dangerous for younger adults, or those in their 20s and 30s. Severely obese white men aged 20 to 30 years live about 13 fewer years than they would be expected to based on estimates from national data. Severely obese white women, or those with a body mass index (BMI) over 45, can expect to live eight fewer years, report researchers in the January 8th issue of the Journal of the American Medical Association.

Obesity also had a profound effect on the lifespan of younger blacks. Obese black men aged 20 to 30 lose about 20 years and obese black women lose about 5 years of life, even after accounting for smoking.

BMI is a measure of weight in relation to height and is believed to be a more reliable gauge of disease risk than weight alone. A person with a BMI of 30 is considered obese, while a person with a BMI between 25 to 29 is considered overweight. To have a BMI of 45, a person who is 5-feet, 4-inches tall would weigh 262 pounds.

In the study, white adults with a BMI of 23 to 25 and black adults with a BMI of 23 to 30 lived the longest.

"Obesity has a profound effect on life span," Dr. David B. Allison from the University of Alabama in Birmingham, and colleagues conclude.

The findings are supported by a second report on more than 3,000 people aged 30 to 49. According to this study, obese, non-smoking women lived seven fewer years and obese, non-smoking men lived about six fewer years than their normal-weight peers did.

Among smokers, obesity reduced life expectancy by about seven years. And obese female smokers lived 13 fewer years and obese male smokers nearly 14 fewer years than non-smoking adults of healthy weight, according to the study.

Together, these reports quantify the health risks associated with obesity, especially for young and middle-aged adults. Considering that about two thirds of the US adult population is overweight or obese, the findings portend an ongoing health crisis, warn researchers.

"The results point to a troubling trend, as rates of overweight and obesity continue on an upward slope in the US," write Dr. Anna Peeters from Erasmus MC in Rotterdam, the Netherlands, and colleagues. "The smoking epidemic in the western world is waning; however, a new fear should be the increasing prevalence of overweight and obesity in young adults, which heralds another potentially preventable public health disaster."

Their study is published in the January 7th issue of the Annals of Internal Medicine.

The authors of both reports call for more research, particularly into the apparent differences in the relationship between obesity and life span between whites and blacks.

Nonetheless, the findings "confirm that obesity is a major public health problem that appears to lessen life expectancy markedly, especially among individuals in younger age groups," Allison and colleagues conclude.

In many cases, obesity and its associated diseases such as type 2 diabetes and high blood pressure may be preventable. The US Centers for Disease Control and Prevention recommends that people trying to maintain good health schedule 30 minutes of moderate physical activity each day, and 60 minutes each day for weight loss.

SOURCE: Journal of the American Medical Association 2003;289:187-193, 229-230; Annals of Internal Medicine 2003;138;24-32.

BMI is an inaccurate measure of obesity or fatness. An athlete or bodybuilder will have a high BMI due to increased muscle mass, but a very low % body fat, and definitely not obese.

That being said, I find it interesting that the suggestion is to increase exercise, which is always a good idea .. and there's no mention of following a lowfat, high-grain diet.

Doreen