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Source: ShutterstockEating habits don’t only affect the body, they affect the mind.

Researchers from Vanderbilt Univ.’s Neuroscience Program in Substance Abuse delved into the mechanisms of overeating, and found a high fat diet results in defective signaling in the central nervous system, leading to increased high-fat food consumption.

“This system can be hijacked by the very foods that it is designed to control. Eating a high-fat or high-carbohydrate diet feels rewarding, but also appears to cause changes in the brain areas involved in controlling eating,” said Aurelio Galli, one of the authors for Vanderbilt Univ.’s study.

Already, obesity and overweightness are worldwide epidemics. Obesity has more than doubled since 1980, according to the World Health Organization, and in 2014, more than 1.9 billion adults were overweight, with 600 million qualifying as obese.

“Feeding is a centrally controlled complex biological behavior fine-tuned by both homeostatic metabolic drive (hunger or satiety) and hedonic motivational drive (reward and salience),” write the researchers in the journal Heliyon. It’s the latter type of feeding that’s dangerous, according to the researchers.

Increased indulgence in high fat diets mess with the insulin signaling pathway in the brain. Using mice, the researchers focused on the protein group rapamycin complex 2 (mTORC2). The mice with genetically altered brain cells, engineered without mTORC2, ate high-fat food excessively. However, when presented with low-fat food, they did not overeat.

“We distilled the neurobiological mechanisms behind overeating high-fat foods for pleasure,” said Kevin Niswender, one of the study’s authors. “We defined the why, where and how of ‘hedonic’ obesity and found that disrupting a specific signaling pathway in the brain can lead to overeating specifically food high in fat.”

Mice without mTORC2 also had less dopamine in areas of their brains. 

Like substance abusers, obesity has been linked with a decreased presence of dopamine in the brain. Previous research from Brookhaven National Laboratory found obese people have fewer dopamine receptors in their brain. “It’s possible that obese people have fewer dopamine receptors because their brains are trying to compensate for chronically high dopamine levels, which are triggered by chronic overeating,” said physician Gene-Jack Wang, who led the Brookhaven National Laboratory study.

“A high-fat diet causes people to eat more,” said Galli. “Our findings reveal a system that is designed to control eating of rewarding foods that are high in fat and possibly sugar.”

Next, the researchers will restore mTORC2 functionality in the obese mice, and see if that leads to a normal intake of calories. 

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