High-Fat Diets May Break The Brain's Ability to Regulate Calories

There are plenty of reasons to limit the amount of fat in your diet, and a new study suggests there's another entry to add to the list: high-fat diets could be messing with your brain's ability to regulate your calorie intake.

In tests on rats, scientists noted that after longer periods of being fed a diet high in fat and calories, the signaling pathway between the brain and the gut apparently gets disrupted, no longer regulating calorie consumption as it should.

Key to this pathway are star-shaped cells in the brain called astrocytes, which normally react to a lot of fat and calories being consumed by putting the brakes on food intake, balancing out what's ingested.

"Over time, astrocytes seem to desensitize to the high-fat food," says Kirsteen Browning, a professor of neural and behavioral science at Penn State College of Medicine.

"[After] around 10-14 days of eating a high fat/calorie diet, astrocytes seem to fail to react and the brain's ability to regulate calorie intake seems to be lost.

This disrupts the signaling to the stomach and delays how it empties."

The rodents used in the research were split into groups and fed a high fat and calorie diet for 1, 3, 5 or 14 days, or a standard control diet. As well as recording food intake and body weight, the team also used genetic editing techniques to target and monitor specific neural circuits, including the astrocytes.

By inhibiting astrocytes in the brainstem, the researchers were able to link these cells to reduced gut-brain communication and lack of food intake regulation that would normally occur during the first 3-5 days of being on a high-fat diet.

They found that inhibited astrocytes mimicked what happened to normal mice after a week or two on a high fat diet.

It's not yet certain exactly how astrocytes are controlling what happens in the gut, but there's clearly some kind of link there.

"We have yet to find out whether the loss of astrocyte activity and the signaling mechanism is the cause of overeating or that it occurs in response to the overeating," says Browning.

While the study only analyzed the eating habits of rats, there's good reason to believe the same applies to human beings as well. With obesity a serious public health concern, experts are looking for ways to better understand and manage it.

Obesity increases the risk of a whole host of health problems, including type 2 diabetes, coronary heart disease, stroke, and certain types of cancer. It's also been associated with depression and other mental health problems.

The researchers are hoping that by discovering more about the "complex central mechanisms" behind the brain's response to over-eating, we'll be able to develop ways to target them and reduce obesity in the future.

"We are eager to find out whether it is possible to reactivate the brain's apparent lost ability to regulate calorie intake. If this is the case, it could lead to interventions to help restore calorie regulation in humans," says Browning.

The research has been published in the Journal of Physiology.

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