Doctors and public health officials have been admonishing us for years that it's unhealthful to carry around extra pounds. A new study quantifies just how much that additional weight increases one's risk of death and finds that being even a few pounds overweight makes a measurable difference.
Researchers analyzed the body mass index, or BMI, of 570,000 white men and women who had never smoked and followed them for an average of 10 years. They concluded that for every 5-point increase in BMI — the equivalent of jumping from the healthy to the overweight category, or from overweight to obese — the chance of dying during the course of the study rose by 31%. The results were published in Thursday's edition of the New England Journal of Medicine.
Considering that two-thirds of Americans are overweight or obese, "even a small increase in the risk of death can be a real public health problem and result in a large number of deaths," said Amy Berrington de Gonzalez, an epidemiologist at the National Cancer Institute and lead author of the study.
Studies have shown that people who are overweight or obese are more likely to develop heart disease, stroke, diabetes and some types of cancer — all conditions that can cause death. But the effect of excess pounds on death from any cause is less clear.
So an international group of researchers combed through 19 studies — most of them designed to investigate cancer — and found data on 1.46 million white adults between the ages of 19 and 84. About 60% of them were excluded from the analysis because they were smokers or former smokers, which complicates the relationship between weight and death, or because they had preexisting health conditions such as cancer or heart disease.
When the researchers zeroed in on healthy women who had never smoked, they found that those with a healthy BMI in the range of 20 to 24.9 had the lowest risk of death during the period of study.
The risk of death increased steadily along with BMI, the researchers found. For overweight women with a BMI between 25 and 29.9, the risk was 13% higher than it was for those in the healthy-weight group. For obese women with a BMI in the 30-34.9 range, the risk was 44% higher, and for those with a BMI between 35 and 39.9, the risk increased by 88%. Among morbidly obese women with a BMI above 40, the risk of death was 2 1/2 times higher than for healthy-weight women.
The risk calculations were similar for healthy men who had never smoked, according to the study. The relative risks were slightly lower when the researchers controlled for variables such as education, alcohol consumption and exercise levels.
Dr. David Heber, director of the UCLA Risk Factor Obesity Program, said the risk calculations would apply to large populations but not necessarily to individuals, since some people can be lean with a BMI above 25 and others can have excess fat even with a BMI below 25.
Applying the findings to nonwhites could also be problematic. For example, he said, "in Asians, even a little excess weight in the abdomen with normal body weight can increase the risk of heart disease."