Eating too much of your favourite junk food may lead to brain changes that stop you enjoying it, a study reveals. Previous research has suggested that people who are obese may take less pleasure in eating than those who are a healthy weight, with brain scans showing reduced activity in pleasure-related regions when presented with food.
Now, scientists at the University of California, Berkeley, have carried out experiments with mice in a bid to discover why this happens. Their study revealed an unexpected brain mechanism which may explain why regularly eating high-fat foods can reduce desire for such products, even when they are easily accessible. And the researchers suggested that losing pleasure in food may actually contribute to the progression of obesity.
Neta Gazit Shimoni, a UC Berkeley postdoctoral fellow, said: “Imagine eating an amazing dessert at a great restaurant in Paris — you experience a burst of dopamine and happiness.
“We found that this same feeling occurs in mice on a normal diet, but is missing in those on a high-fat diet. They may keep eating out of habit or boredom, rather than genuine enjoyment.”
When observing the mice, Ms Gazit Shimoni noticed a surprising trend. When in their cages, the mice preferred high-fat food with 60% fat over normal food with 4% fat.
But when released and given access to high-calorie foods such as butter, peanut butter and chocolate, they showed less desire to indulge than mice with a normal diet.
Brain tests then showed that the mice eating a high-calorie diet had reduced levels a brain peptide called neurotensin which interacts with the dopamine network.
Professor Stephan Lammel, an expert in neuroscience at UC Berkeley, siad: “Neurotensin is this missing link. Normally, it enhances dopamine activity to drive reward and motivation.
“But in high-fat diet mice, neurotensin is downregulated, and they lose the strong desire to consume high-calorie foods — even when easily available.”
When the mice’s neurotensin levels were restored, they both lost weight and showed more interest in high-calorie foods.
Prof Lammel added: “Bringing back neurotensin seems to be very, very critical for preventing the loss of desire to consume high-calorie foods.
“It doesn’t make you immune to getting obese again, but it would help to control eating behaviour, to bring it back to normal.”
The researchers hope their findings could pave the way for new obesity treatments. “A natural inclination toward junk food is not inherently bad — but losing it could further exacerbate obesity,” Prof Lammel said.
“A high-fat diet changes the brain, leading to lower neurotensin levels, which in turn alters how we eat and respond to these foods.
“We found a way to restore the desire for high-calorie foods, which may actually help with weight management.” The findings were published in the journal Nature.
