The study was supported by the National Heart, Lung, and Blood Institute (NHLBI), one of the National Institutes of Health (NIH).

The researchers analyzed the long-term risk of developing overweight and obesity among 4,000 30-to-59-year-old participants in NHLBI's landmark Framingham Heart Study, who were followed from 1971 to 2001.

Risk May Be Underestimated

"National surveys and other studies have told us that the United States has a major weight problem, but this study suggests that we could have an even more serious degree of overweight and obesity over the next few decades," says NHLBI Director Elizabeth G. Nabel, MD, who also co-chairs the NIH Obesity Research Task Force.

Currently, 65 percent of US adults aged 20 years and older are either overweight or obese, according to the National Center for Health Statistics, part of the Centers for Disease Control and Prevention. Approximately 30 percent of adults are obese.

"In addition, these results may underestimate the risk for some ethnic groups," she notes, since all of the Framingham participants were white. Other studies have shown that Hispanic and black individuals, especially women, have a greater prevalence of excess weight compared to their white counterparts.

Wake-up Call

Framingham researchers assessed the participants’ body mass index (BMI) – a standard measure of weight relative to height, which is an indicator of total body fat. A BMI of 18.5 to 24.9 is considered healthy for adults. Those who have a BMI of 25 to 29.9 are overweight, while obesity is indicated by a BMI of 30 or higher.

Making it to middle age without extra pounds was no guarantee for staying at a healthy weight, even in the short term. About one in five women and one in four men who were at a healthy BMI at a routine Framingham study examination became overweight after four years.

Among those who were overweight, 16 to 23 percent of women and 12 to 13 percent of men became obese within four years.

"Our results, although not surprising, are worrisome," comments Ramachandran Vasan, MD, Associate Professor of Medicine at Boston University School of Medicine and lead author of the study. "If the trend continues, our country will continue to face substantial health problems related to excess weight," he warns.

"Overweight and obesity increase the risk of poor health," adds Nabel.

"We hope these results will serve as a wake-up call to Americans of all ages. Even those who are now at a healthy weight need to be careful about maintaining energy balance to avoid gaining weight," she explains. "Taking simple steps to make sure that the overall number of calories you consume do not exceed the amount you burn can play a major role in lowering your risk for many chronic conditions."

Losing 10% of Body Mass Helps

Overweight increases the likelihood of developing diabetes, high blood pressure and heart disease, stroke, asthma and sleep apnea, some cancers, osteoarthritis, and gall bladder disease. Obesity is associated with with early death.

Even a small weight loss -- just 10 percent of body weight -- can help people who are overweight or obese lower their risk of developing many serious health conditions.

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