We don’t think much of overeating. Bigger portions are never something to complain about, even if the food itself isn’t all that great. We might not even notice when we do it ourselves, when it’s symptomatic of a physical illness like Type 2 diabetes, let alone due to other causes like depression or binge eating disorders.
Consequently, it’s easy to think that these are yet more problems that we can simply fix by cutting back on what we eat — that we can stop whenever we want to.
Unfortunately, the same brain activity linked to excessive gambling and most addictions is also at work with compulsive overeating. While the search is still on for all of the brain circuitry involved in overeating, researchers have made a significant step towards getting closer.
A new study at the University of Georgia, Athens (UGA) has identified one crucial part of the circuit. A transmitter called “melanin-concentrating hormone” (MCH), which when elevated in the brain can cause the body to eat more ravenously, and now, according to a new paper published in the journal Nature Communications, also increases impulsiveness.
“There’s underlying physiology in your brain that is regulating your capacity to say no to impulsive eating,” said the study’s lead author, Dr. Emily Noble. Noble, who is an assistant professor at the UGA College of Family and Consumer Sciences, knew that a buildup of MCH could increase the appetite, but this study allowed her and fellow researchers to isolate the exact mechanism involved.
They used trained lab rats for their study who had previously learned how to operate a lever. The lever would open a door and release a tasty reward: a pellet high in both fat and glucose, the two things that might sound familiar to your own cravings — why a peanut butter and jelly sandwich (ideally on buttered toast) could seem like the perfect storm to satisfy our hunger. Before they were brought into the lab, the rats learned to wait 20 seconds for each treat. Pressing the lever too soon meant they’d be forced to wait an extra 20 seconds before they’d be rewarded.
Afterwards, the researchers targeted a specific MCH neural pathway in each of the rats, protruding from the hypothalamus, which regulates hunger, to the hippocampus, a region of the brain concerned with learning and memory function before placing them back in the chambers. The subsequent results suggested that MCH doesn’t necessarily require that rodents liked the food, and working harder for the food didn’t do anything to influence levels of MCH either.
Instead, the circuit targeted the rats’ ability to stop themselves from trying to acquire more food. Once they were given a reward, their brains no longer processed a signal that they no longer had any use for it.
“Activating this specific pathway of MCH neurons increased impulsive behavior without affecting normal eating for caloric need or motivation to consume delicious food,” says Noble. She hopes that in the not too distant future, we’ll be able to program this circuit on our own, and allow for people to follow diets without having to resort to options that could reduce appetite or deprogram them from enjoying their favorite foods.
