Eating a high quantity of fatty foods could throw your brain's hunger signalling awry, causing you to want more even if you don't need it and gain weight, according to recent research.
To make sure you eat what you need to survive, your body's chemistry associates eating with pleasure, but when that balance gets thrown out of whack, obesity results, say the researchers.
"We defined the why, where, and how of 'hedonic' obesity and found that disrupting a specific signalling pathway in the brain can lead to overeating specifically food high in fat," says co-author Dr. Kevin Niswender, emphasising the word "hedonic," which means guilty pleasures.
On a global scale, obesity has more than doubled since 1980, making for a total of more than two billion overweight individuals worldwide in 2015, 600 million of whom are obese.
"We have always been struck by how much animals, and even people, will over-consume tasty high-fat foods, even though they might be technically feeling full," says co-author Dr. Aurelio Galli of Vanderbilt University in the US.
In the study, the researchers observed the insulin-signalling pathway in the brain and its effect on certain cell circuits, knowing that problems with insulin signalling can lead to obesity.
Targeting a group of proteins involved in the insulin-signalling pathway called Rapamycin complex 2 (mTORC2), they removed it from the brain cells of mice.
Once missing these proteins, the mice chowed down on high fat foods unreasonably, yet when only low-fat food was available, they did not overeat, according to the study.
What's more, dopamine levels plunged for the mice deprived of their mTORC2 proteins, which is in line with prior research associating lower dopamine transmission with obesity in humans.
"Our findings reveal a system that is designed to control eating of rewarding foods that are high in fat and possibly sugar," says Dr. Galli. "This system can be hijacked by the very foods that it is designed to control."
When signalling in parts of the brain that control eating goes awry, it leads to a vicious cycle, prompting more and more fatty-food intake that only reinforces the brain's hunger, says Dr. Galli.
The next step for the researchers is to give the now-obese mice back their mTORC2 proteins and see whether they go back to eating normally.