Obesity isn't always due to poor physical activity and eating habits. Most of the time the body starts storing more fat than it should and burns fewer calories. Sanford-Burnham researchers have now proposed that maybe a protein called p62 leads to the body storing unhealthy fat.

The study found that when the protein p62 was missing in the fat tissue, the body started storing white fat that is bad for the body. They found that this happens because of the metabolic shift in the body.

"Without p62 you're making lots of fat but not burning energy, and the body thinks it needs to store energy. It's a double whammy," said Jorge Moscat, Ph.D.

Earlier, Moscat's team studied mice that lacked the p62. They found that these mice weighed more and had other health complications like diabetes and hypertension than mice with p62. However, in this study mice lacked the protein in all tissue, so researchers weren't sure the lack of protein in which tissue led to obesity.

In the current study, researchers pinpoint the tissue that is associated with obesity. They made mouse models that lacked p62 protein in specific organs or tissue like central nervous system, the liver, or muscles. But, mouse models in all cases weighed normal and weren't obese.

It was then that researchers found that mice models that lacked the protein in a specific tissue - the fat tissue - were more likely to get obese than others. These mice displayed all symptoms of obesity just like the mice that lacked p62 in all tissues.

Further research showed that p62 induces obesity by inhibiting enzyme ERK while activating another enzyme called p38.

The absence of p62 makes enzyme p38 less active in brown fat while ERK is more active in white fat.

Fat tissue is easily accessible and therapeutics targeting fat cells can help fight obesity. "This makes it easier to think about new strategies to control obesity," Moscat said.

The study is published in the Journal of Clinical Investigation.