Depressed because you're fat? It's not just because of the way you look.

There is plenty of data that demonstrate a correlation between people who are overweight and/or obese and their level of depression. Now a recent study in mice demonstrates that those who are obese are likely not depressed just because of the way they look but that eating a high-fat diet results in changes in brain chemistry that are directly correlated to depressive behaviors. Mice chronically fed a high-fat diet exhibit enhanced depressive behavior as evidenced by numerous stress-related tests. For example depressed mice will spend much less time out in the open or walking across an elevated platform. Both in mice and humans there is a correlation between excessive intake of energy-rich foods, such as high-fat and/or high-sugar diets, and changes in the reward circuitry in the brain.

This work was recently published in the International Journal of Obesity:

The neural circuits that underlie motivation and reward are composed of dopamine releasing neurons in regions of the midbrain called the ventral tegmental area (VTA) and the substantia nigra that innervate the limbic system, specifically the dorsal striatum and the nucleus accumbens (NAc). The limbic system is the area of the brain that supports a variety of functions including emotion, behavior, and motivation as well as others. Evidence in animal models of obesity as well as in obese humans shows reduced dopamine signaling in the striatum. In addition to its role in motivation and reward in the limbic system, dopamine is involved in the pathophysiology and the etiology of mood disorders including depression.

These results highlight the fact that chronic consumption of high-fat diets (as well as high-sugar diets) leads to negative changes in brain circuits that regulate mood. So, not only are many people who are overweight and/or obese depressed due to low self esteem, they are propagating a viscious cycle of eating and depression and eating more because of alterations in their brain chemistry. This means that it is highly likely that getting in control of ones diet and weight will result in positive benefits not only in their physical well-being but also in their mental well-being.



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