Magazine article Science News

Brain May Subvert Efforts to Diet: In Obese, Hunger Signals Can Persist Even after a Meal

Magazine article Science News

Brain May Subvert Efforts to Diet: In Obese, Hunger Signals Can Persist Even after a Meal

Article excerpt

In obese people, even when the brain knows the body isn't hungry, it responds to food as if it were, new brain-scan data show. That means that when obese people try to shed weight, they may find themselves on the losing side of a battle with neural centers that unconsciously encourage eating.

For instance, in normal-weight people a neural reward system that reinforces positive feelings associated with food turns off when levels of the blood sugar glucose return to normal after a meal--a signal that the body's need for calories has been sated. But in obese people, that reward center in the central brain turns on at the sight of high-calorie food even when blood sugar levels are normal.

"The regulatory role of glucose was missing in the obese," says Elissa Epel of the University of California, San Francisco, an obesity researcher not involved with the new study. She says the data might "explain the drive to eat that some obese people feel despite how much they've eaten."

For the study, nine lean and five obese adult volunteers viewed pictures of foods such as ice cream, french fries, cauliflower or a salad while undergoing brain scans. Throughout the procedure, researchers asked the recruits to rate their hunger and how much they wanted a particular item.

Volunteers arrived for their brain scans several hours after eating, and the researchers used insulin pumps to establish volunteers' blood sugar levels at either normal background values (roughly 90 milligrams per deciliter), or at the "mild" end of low (around 70 milligrams per deciliter). …

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