WEDNESDAY, Sept. 7, 2011 (HealthDay News) -- Carrying extra weight, especially around the middle, is a risk factor for death among black women, according to a new study.
And the heavier a woman is, the greater her risk of dying sooner than her normal-weight peers.
"The risk of death increased incrementally with rising body mass index (BMI). Once women were above normal weight, they had an increased risk of death," said the study's senior author, Dr. Julie Palmer, a professor of epidemiology at the Slone Epidemiology Center at Boston University.
In addition, she said, "independent of BMI, women who had a higher waist circumference had an increased risk of death. And, this finding was primarily in normal-weight women."
Palmer said as women gain weight, the health risks of obesity may diminish the impact of a larger waist on the risk of death.
Results of the study are published in the Sept. 8 issue of the New England Journal of Medicine.
Overall obesity and abdominal obesity are both increasing rapidly in America. It's projected that by 2020, as many as 70 percent of black women in America will be obese and up to 90 percent will have abdominal obesity, according to background information in the study.
Some previous research had suggested that obesity might not increase the risk of death as much for black women as it does for white or Asian women in America. Authors of the current study suspected that other factors, such as smoking or socioeconomic status, might have mitigated the actual effects of obesity on the risk of death in black women.
The current study included data from the Black Women's Health Study, a national sample of almost 52,000 black women in America. The women were between the ages of 21 and 69 when they enrolled in the study, and none had a history of cancer or heart disease.
The study began in 1995 and continued through 2008. The women were contacted every two years during the study.
During that time, 770 women who had never smoked died. In nonsmokers, the researchers found that the risk of death was lowest for those who had a BMI in the range of 20 to 24.9, which is considered normal. (BMI is an estimate of body fat using height and weight.)
As soon as women crossed the threshold to overweight, however, the risk of dying increased. For women with a BMI of 25 to 27.4, the risk of death was 12 percent higher than for women with a normal BMI. With a BMI of 27.5 to 29.9, nonsmoking black women had a 31 percent increased risk of death.
At 30 to 34.9 -- a BMI of 30 is considered obese -- nonsmoking black women faced a 27 percent higher risk of death. When BMI reached 35 to 39.9, the risk of death increased to 51 percent higher compared to women of normal BMI. Women whose BMIs were 40 to 49.9 faced a death risk more than double that of a normal-weight woman.
The researchers also found an association between a larger waist circumference and the risk of death, though this link was strongest for women who had a BMI under 30. After adjusting for BMI, the researchers found that women with waists between 40 and 47 inches had a 40 percent higher risk of death than did women whose waists were 26 to 27 inches, according to the study.
"BMI is just a number. The distribution of the fat means something," explained Dr. Mitchell Roslin, chief of bariatric surgery at Lenox Hill Hospital in New York City.
"When you see people who have larger hips and buttocks, they usually don't have diabetes or cardiac disease, but they have a high risk of joint disease and other problems. People who are apple-shaped tend to have more cardiac disease and diabetes, and we used to think it was just the apples that we had to worry about, but now we know it's just different problems," he said.
"The take-away from this is that we all need to eat healthier. The healthiest foods come from in the ground, not the middle aisles of the supermarket. And, physical fitness mitigates a lot of risk," Roslin added.
He also said it's important to realize that losing any weight is helpful, even if you're still in a higher risk category. "If a woman with a BMI of 33 lowers it to 28, she still has a higher risk according to the study, but she will feel so much better," Roslin said.
Learn more about the health risks of being overweight from the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.