EXCESS BODY FAT, ESPECIALLY IN THE ORGANS, MUSCLES, & BONES, INCREASES THE RISK OF OSTEOPOROSIS

It was once believed that excess body weight decreased risk for low bone density known as osteoporosis.  However recent studies indicate that being obese actually increases the likelihood of having inadequate bone density. A number of recent studies have found that excess fat in the abdomen, particularly fat deposited between the organs, increases osteoporosis risk.  Adding to these findings, a new study lead by Dr. Miriam Bredella at Massachusetts General Hospital has found that excess fat in the blood, liver and muscle is especially linked with greater fat in the bone marrow, and reduced bone density. 

In Dr. Bredella's study, researchers used magnetic resonance spectroscopy (MRS) to assess fat in more than 100 obese but otherwise healthy men and women, ages 19-45.  MRS allowed them to accurately assess levels of fat in the liver, muscles, and bone marrow.   The MRS results showed that people with more liver and muscle fat had higher levels of fat in their bone marrow, independent of body mass index, age, and exercise status.  Levels of fats in the blood also correlated with increased bone marrow fat.  Specifically, elevated blood levels of triglycerides and lower “good” HDL cholesterol were strongly associated with higher levels of fat in the bone marrow.     

Researchers are still trying to understand how excess fat impairs bone health.  Excess fat tissue in the bones appears to displace mineralized bone tissue. Cells in the bone marrow are stem cells that can develop into different kinds of cells including bone building cells, osteoblasts, and fat cells, adipocytes.  When there are high levels of fat in the blood, it appears that more stem cells are devoted to becoming fat stores and fewer develop into bone builders.  Additionally, high levels of fat in the blood, especially elevated triglycerides, appear to stimulate osteoclasts, the cells responsible for breaking bone down.

What to do:  Besides excess fat between the organs and in the liver, muscles, and blood, some of the other risk factors for osteoporosis include being female, advanced age, a family history of osteoporosis, inactivity, being underweight, vitamin D deficiency, and inadequate intake of calcium.  Many medicines and health problems also increase your risk.  It is recommended that women over 65 and younger post-menopausal women with risk factors for low bone density get a dual energy x-ray absorptiometry (DEXA) scan of their bones.  Discuss the status of your bone health with your provider.  To help prevent osteoporosis, maintain a healthy weight and blood cholesterol levels, get regular weight bearing activity (such as lifting weights, walking), have your doctor monitor your vitamin D levels and supplement when necessary, and include plenty of foods rich in calcium such as nonfat/lowfat dairy and dark green vegetables.

Adapted from article available at:

http://www.nlm.nih.gov/medlineplus/news/fullstory_138755.html

http://www.sciencedaily.com/releases/2013/07/130716080021.htm

Sources:

Radiological Society of North America, news release, July 16, 2013.  Available at:  http://www2.rsna.org/timssnet/media/pressreleases/pr_target.cfm?ID=681

Bredella MA, Gill CM, Gerweck AV, et al. Ectopic and serum lipid levels are positively associated with bone marrow fat in obesity radiology. Radiology, 2013; DOI: 10.1148/radiol.13130375.  Available at: http://radiology.rsna.org/content/early/2013/06/27/radiol.13130375.