Women who pack weight around their waists instead of on their buttocks and thighs have an increased risk of dying prematurely, according to the largest study yet to look at the association between abdominal fat and death.
The study of 44,636 women released online by the journal Circulation found that women with the largest waists -- 35 inches or greater -- had a 79% higher chance of premature death compared with women whose waists measured 28 inches or less. The risk was adjusted for multiple health factors.
Women with the largest waists had twice the risk of dying of cardiovascular disease -- even if their weight was normal -- and a 63% greater chance of dying of cancer compared with women with smaller waists, according to the report.
The study, conducted by researchers at Harvard University and Brigham and Women's Hospital in Boston, adds to the growing evidence that belly fat can pose serious health risks, even for those who are not obese.
Last month, research in the journal Neurology found that people who had large guts during midlife were at greater risk of developing dementia in old age.
Other previous studies have detected a link between abdominal fat and the risk of diabetes, stroke and heart disease.
Richard N. Bergman, an obesity researcher at USC not connected to the report, said that the results were not a surprise, given the severity of the illnesses linked to belly fat. The message is that people should watch their waist circumference as well as the scale, he said.
"People can be very comfortable with their weight and not be aware that due to their waist circumference they are at increased risk," he said.
Although only women were studied, Bergman said, men with large bellies probably also face a higher risk of death.
The report was based on data drawn from the Nurses' Health Study, which has monitored the medical history of participants since 1976.
Researchers in the latest study tracked women for 16 years. The average age was around 50.
The participants measured their waists and hips at the start of the study, and every two years completed questionnaires about their health, including activity level, smoking habits, diet, blood pressure and cholesterol.
During the study, 3,507 women died, including 1,748 from cancer and 751 from heart disease.
Women with the largest waists who were also obese -- as defined by body mass index, a ratio of height and weight -- were at the greatest risk of premature death, researchers said.
A 5-foot-5-inch person who weighs 180 pounds has a BMI of 30 and is considered obese.
Lead author Dr. Cuilin Zhang, a researcher at the National Institute of Child Health and Development, said no one knows why abdominal fat seems to be particularly dangerous.
One theory is that abdominal fat exposes nearby organs to potentially toxic chemicals produced by the fat, said Zhang, who conducted the research while at Harvard.
Fat that collects on the buttocks and thighs may be less hazardous because it is more distant from the liver, pancreas and other abdominal organs, she said.
Zhang said researchers also want to identify genes or other factors that cause people to tend to accumulate belly fat.
About half of the nation's adults have an unhealthy amount of belly fat, according to previous studies.