Scientists Identify Hormone that Makes Us Eat When We’re Already Full
If we all stopped eating once sated then none of us would become overweight. Unfortunately, many of us will continue to eat something tasty even after we’re full. Scientists think they’ve identified the hormone that makes us do this and have shown that if they blocked it – we probably wouldn’t overeat anymore.
Scientists at UT Southwestern Medical Center think they know why people continue to eat high fat or high calorie foods, even after they’re otherwise sated (think cheesecake at the end of a big meal!).
They say we do this because of the influence of a hormone called ghrelin.
Researchers have previously shown that high levels of ghrelin in the body increase the pleasure experienced after consuming cocaine or alcohol. The Southwestern UT researchers figured that since eating stimulates the same pleasure systems in the brain as alcohol and cocaine, that ghrelin may also influence our eating habits.
To find out, they gave some mice an injection of ghrelin and gave nothing to a group of control mice. All mice had just eaten their fill. The mice then had a choice to spend time in one of two rooms – one room had previously been a source of high fat ‘desirable’ food whereas the other room had previously been a source of regular low fat food.
- The sated mice that had not been injected with ghrelin had no preference between the rooms, spending equal time in both.
- The mice injected with ghrelin spent far more time in the room that had once provided high fat food – hoping to find more!
Lead researcher, Dr. Mario Perello explained why the mice acted as they did, saying, "We think the ghrelin prompted the mice to pursue the high-fat chow because they remembered how much they enjoyed it. It didn't matter that the room was now empty; they still associated it with something pleasurable."
High levels of ghrelin increase the pleasure we experience from food (and drugs and alcohol) and increase our motivation to experience this pleasure. With high levels of ghrelin, we are more likely to eat when we are already full and will go to greater lengths to secure food.
This latest experiment is another in a series of recent experiments showing physiological parables between the root causes of addictive behaviors and overeating. Whether compulsive eating can be considered an addiction is a contentious question, but it seems clear that ghrelin and a deep searching for pleasure lie intertwined at the root of behaviors ranging from drinking too much alcohol to eating too much high calorie food.
The scientists now call for further research into the neural processes that regulate ghrelin.
The full research results can be found in the online edition of Biological Psychiatry.