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High BMI Linked to Higher Risk of Death

Article date: December 2, 2010

By Rebecca Snowden

Being obese – that is, having a body-mass index (BMI) greater than 30 – or overweight significantly increases your risk of dying, regardless of whether you smoke or have a serious illness like cancer, according to a report published today in the New England Journal of Medicine. Having a BMI between 20.0 and 24.9 – within the range considered normal -- is associated with the lowest risk of death, the researchers found.

While some studies have found a strong relationship between high body-mass index and an increased risk of death, other reports have suggested that having a bit of excess body fat might be beneficial. This study, which combines data from 19 different studies and included over 1.4 million people, provides strong evidence that excess body fat is detrimental to your health. The report was co-authored by the American Cancer Society (ACS).

"There is overwhelming evidence that being obese is harmful to one's health and survival,” said Michael J. Thun, MD, American Cancer Society vice president emeritus of epidemiology. “Approximately one in three Americans age 20 and older is obese. What has been less clear is whether being overweight (BMI 25-29.9) also shortens life. This new analysis finds that being overweight, like being obese, was associated with increased risk of dying from all causes combined.”

A Big Problem

More and more Americans are overweight or obese, thanks to bigger food portions; the overabundance of cheap, unhealthy foods; and sedentary lifestyles. About 1 out of 3 American adults is now obese, and another 1 out of 3 is overweight. Even more alarming, 17% of women and 11% of men are severely obese – that is, they have a BMI of 40 or more.

This study shows just how much of an impact excess body weight is having on Americans’ health. Researchers combined data from 19 long-term studies and controlled for factors such as smoking to isolate the relationship between BMI and the risk of death. This analysis was restricted to non-Hispanic white non-smokers aged 19 to 84.

“By combining data on nearly 1.5 million participants from 19 studies we were able to evaluate a wide range of BMI levels and other characteristics that may influence the relationship between excess weight and risk of death,” said Amy Berrington de Gonzalez, National Cancer Institute, lead author of the study. “Smoking and pre-existing illness or disease are strongly associated with the risk of death and with obesity. A paramount aspect of the study was our ability to minimize the impact of these factors by excluding those participants from the analysis.”

High BMI, High Risk

BMI is based on your weight and height. Current guidelines from the U.S. Centers for Disease Control and Prevention and the World Health Organization define underweight as having BMI of less than 18.5. A BMI between 18.5 and 24.9 is in the normal range. A person with a BMI between 25 and 29.9 is considered overweight, while a person with a BMI of 30 or more is considered obese.

The researchers found that the higher the BMI, the higher the risk of death. Study participants with a BMI of 30.0 to 34.9 had a 44% increase in risk compared to those in the 22.5 to 24.9 range. The risk increased as BMI increased. Compared to participants in the normal weight range, those with a BMI of 35.0 to 39.9 had an 88% increase in risk, and those with a BMI over 40 had a 250% increase in risk. For every 5 unit increase in BMI, the researchers observed a 31% increase in risk of death.

Those patterns held regardless of other factors like alcohol use, physical activity level, and education level.

Lower Your BMI

“While evidence is becoming abundantly clear that being overweight and obese is a serious health risk, we still face an enormous challenge in finding out how best to help people maintain a healthy body weight,” says Thun.

To lower your BMI, the American Cancer Society recommends balancing calorie intake with physical activity. Eat at least 5 servings of fruit and vegetables every day, choose whole grains over processed grains, and limit red meat. Adults should engage in at least 30 minutes of moderate or vigorous physical activity 5 days a week or more.

Of course, that’s easier said than done. For help, see these tips and tools.

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