Excess Fat in Organs and Blood Could Increase Risk of Osteoporosis

In addition to excess stomach fat, a new study has determined that too much fat around the liver and muscle as well as in the blood could leave individuals at risk of osteoporosis.

Published in the journal Radiology, the report found that obese people with higher levels of fat in these three areas also exhibited higher amounts of fat in their bone marrow, which has been found in recent years to be inversely related to bone density.

"Bone marrow fat makes bones weak," study lead author Dr. Miriam A. Bredella, a radiologist at Massachusetts General Hospital and associate professor of radiology at Harvard Medical School in Boston, said in a press release. "If you have a spine that's filled with fat, it's not going to be as strong."

While other studies have examined the relationship between visceral fat and bone mineral density, this study is unique in that it specifically looked at fat inside bone marrow.

"In our study, we focused on bone marrow fat because that is where our stem cells can develop into osteoblasts - the cells responsible for bone formation - or fat cells," Dr. Bredella said. "We also wanted to look at the relationship between bone marrow fat and other fat components, such as those in the liver and muscle."

In order to carry out the study, Dr. Bredella and colleagues used proton magnetic resonance spectroscopy (MRS), a technique that precisely measures fat, to examine 106 obese men and women, ages between 19 and 45 years who were otherwise healthy.

The results showed that people with more liver and muscle fat had higher levels of fat in their bone marrow, regardless of their body mass index, age or even how much they exercised.

Moreover, triglycerides, the type of fat found in the blood, also had a positive correlation with bone marrow fat. The reason for this, the researchers hypothesize, possibly resides in their ability to stimulate osteoclasts, a type of cell that breaks up bone tissue.

The team also discovered that HDL cholesterol, the "good" type of cholesterol associated with a lower risk of heart disease, was inversely associated with bone marrow fat content.

Going forward, Dr. Bredella said that more research is needed to further clarify the mechanism behind this differentiation of stem cells, noting that cell-signaling molecules called cytokines are known to promote the conversion of stem cells into fat.

"Obesity can shift stem cell lineage, resulting in more bone marrow fat," she said.