Our body is designed to perform the balancing act when it comes to food. It controls the food intake by striking a balance between the body's need for food to survive and its desire for food for pleasure. However, a new study published in the new open access journal Heliyon, has revealed that faulty brain signaling can cause overeating of high fat foods in mice, leading to obesity. Due to a tweak in the balance of the brain signaling system, pleasure can override need and it can lead to overeating and subsequently to obesity.
The researchers at the Neuroscience Program in Substance Abuse (N-PISA) at Vanderbilt University, USA opines that if we can understand the mechanisms behind overeating, incidences of obesity could be reduced or prevented.
Dr. Aurelio Galli, one of the authors of the study said that scientists have observed that animals as well as humans tend to over-consume tasty high-fat foods, even though they have a feeling of being full. One of the important factor in this phenomenon is a high fat diet – it causes obese people to eat more, which skyrockets their caloric intake and their weight loss goals goes for a toss. Several studies have been conducted to understand why a high fat diet has such an effect.
Since 1980, obesity has doubled worldwide. It is estimated that 2 billion people are overweight of weight 600 million people are obese. Economic stresses, changes in environment and changing food trends all contribute to obesity.
Obesity occurs when due to faults in the central nervous system; our body can’t match its energy intake through food with its energy expenditure. The new study reveals a novel mechanism that leads to overeating high fat foods for pleasure. A specific signaling pathway in brain cells that is in charge of controlling motivation, movement and attention determines the amount of high fat foods consumed. When there is a fault in this signal, the person only overeat high fat foods.
Dr. Kevin Niswender, one of the authors of the study said that they distilled the neurobiological mechanisms involved specifically in overeating for fat. They defined the basics of ‘hedonic’ obesity and found that disrupting a specific signaling pathway in the brain can lead to overeating specifically food high in fat. That specific signaling pathway in the brain is insulin signaling. Study revealed that insulin signaling can override the body’s natural homeostatic mechanisms in favor of the reward mechanisms, leading to obesity.
Rapamycin complex 2 (mTORC2) is a group of proteins involved in insulin signaling in the brain. The researchers researched further to find out how insulin signaling and mTORC2 affect overeating of high fat foods. For this the researchers genetically altered brain cells in mice by taking out a part of mTORC2 and found that the mice without a functioning mTORC2 ate high-fat food excessively. But, when provided only with low-fat food they did not overeat. They also found that the mice whose mTORC2 does not function also had less dopamine in specific regions of the brain. It is known that lower dopamine transmission in brain cells is associated with obesity in humans and animals, and also in escalating substance abuse.
Dr. Galli opined that their studies reveal that the system designed to control eating high fat food in the brain can be hijacked by the very foods that it is designed to control. This can lead to a vicious cycle of increase in high-fat diet intake which further cements changes in these brain areas. The next step in the researcher's study is to find out if disrupting the signaling system works. And also to find out what happens when they restore mTORC2 signaling in obese mice. Does it lead to them eating a normal amount of calories? Only further research can reveal it.
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