TUESDAY, Nov. 30, 2010 (HealthDay News) -- Not only does extra weight around the middle increase a woman's risk of heart disease and diabetes, new research suggests it also ups a woman's risk of developing osteoporosis.
In a study of 50 premenopausal women of various sizes, Harvard researchers found that women who had more fat around the abdomen were more likely to have lower bone mineral density, which can eventually lead to osteoporosis.
"All fat isn't the same. Tummy fat has a damaging effect on bone health," said the study's lead author, Dr. Miriam Bredella, a radiologist at Massachusetts General Hospital and an assistant professor of radiology at Harvard Medical School in Boston.
Bredella was slated to present the findings Tuesday at the annual meeting of the Radiological Society of North America in Chicago.
As many as 10 million Americans, most of them women, have osteoporosis, according to the U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Another 34 million Americans have low bone mass, putting them at risk of developing osteoporosis, reports NIAMS.
Risk factors for osteoporosis include a deficiency in estrogen, a diet lacking in calcium and vitamin D, eating disorders, certain medications, a sedentary lifestyle, drinking too much alcohol and smoking, according to NIAMS.
But extra weight was previously believed to somewhat protect against bone loss, said Bredella.
The average body mass index (BMI) of the women recruited for the study was about 30, with scores ranging from 19 to 46. A BMI of 18.5 to 24.9 is considered normal, while a BMI of 25 to 29.9 is considered overweight. A BMI of 30 or more is considered obese, according to the U.S. Centers for Disease Control and Prevention.
All of the women underwent a special imaging technique called MRI spectroscopy that allowed the researchers to accurately measure fat deposits, including fat found in the bone marrow.
Women who had more visceral fat, meaning fat around the mid-section, were more likely to have a lower bone mineral density. In addition, an association between visceral fat and the levels of bone marrow fat was noted.
"Visceral fat is deep belly fat, and it's been found to be bad for heart disease and diabetes. This type of fat releases fatty acids into the liver, and it also releases other substances and hormones that have an effect on the heart and the pancreas, and also probably on bones," said Bredella. "But, we don't know exactly what it is in visceral fat that causes problems."
As for the increase in bone marrow fat, "a lot of bone marrow fat makes the bone weak," Bredella said.
"This study is more bad news for obesity. The one good thing we thought obesity might do -- protect the bones -- isn't true," she added.
"This is a fascinating study that raises interesting and important questions," said Dr. Judi Chervenak, an associate clinical professor of obstetrics, gynecology and women's health at Montefiore Medical Center and the Albert Einstein College of Medicine in New York City.
"Being a healthy weight and trying to control visceral obesity is becoming important from so many different angles," she stated. "You need to make lifestyle changes that focus on overall health and wellness, and exercise is very important for helping prevent osteoporosis and other illnesses. If you haven't been moving, just try to get out and go for a walk. Ideally, you'll work up to regular exercise, but get out and get some exercise," she advised.
Bredella said the researchers are currently studying fat distribution and bone mineral density in men to see if the patterns hold true for both sexes.
To learn more about osteoporosis and ways to prevent it, visit the U.S. National Institute of Arthritis and Musculoskeletal and Skin Diseases.