Why Stored Fat Is Hard to Lose

By Michael Cole

A study has found evidence which suggests that the more fat a person carries, the more the body resists burning it. This is due to a protein produced in the body with extra stored fat. The protein acts as an inhibitor to fat burning, which may lend new insight into the development of anti-obesity treatments as well as treatments for other metabolic conditions.

Different Types of Fat Cells

Fat cells in the body can be divided into two types. First are the typical fat cells called white adipocytes; they have the job of storing energy until it's needed, at which point it's released through physical activity. The other type of fat cells are known as brown adipocytes, which differ from the first group in that rather than supply the body with energy, their primary function is to keep the body warm through a process medical science calls thermogenesis. The latest research, however, has discovered a protein in the body that blocks this process from happening.

The Skinny on the Study

The study focused on mice that were genetically selected to not produce this protein, known as sLR11. The mice that lacked the sLR11 protein proved to be much less likely to gain weight than mice that did have it. Typically, when mice, or humans, begin to take in more calories their metabolic rate goes up. However, in mice that lacked the sLR11 protein, their metabolic rates skyrocketed when given more calories, meaning they were able to burn calories much faster. 

Looking more closely at these mice, it was found they had genes that normally should be linked to fat cells providing thermogenesis, but for some reason were instead linked up to fat cells providing energy release. As a result, these mice released energy at higher rates, especially when eating a high fat diet. 

Observations showed that the sLR11 protein that inhibits fat burning binds to receptor sites on fat cells, much as a key fits into a specific lock, and this binding is what causes the cells to be unable to burn up energy for fat reduction. This protein is effectively a signal to fat cells which says “store your energy up for future use and don’t go wasting any of it by releasing heat!”

Looking from mice to humans, the researchers found that, sure enough, overweight humans had higher levels than average of this protein freely circulating in their blood. Where this protein comes from is uncertain, but researchers suspect that it is produced by fat cells themselves. 

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