Obese woman measures her waist with a measuring tape in casual clothing on a white background.

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KRAKOW, Poland — High-fat diets would seem to be an obvious trigger for obesity. While a new study finds this appears to be true, researchers say fatty foods don’t lead to excessive weight gain exactly how you think they might. Researchers from Poland and the United Kingdom find a high-fat diet actually disrupts the brain’s body clock, throwing off its ability to tell someone they’re full.

In an experiment with rats, study authors discovered that consuming a high-fat diet affects the brain’s control over the body’s daily rhythms, including the production of certain hormones and appetite. In the past, scientists believed the “master body clock” resided in the brain’s hypothalamus. However, new research has revealed that the control of certain body functions (like appetite) lies in another area — a group of neurons called the dorsal vagal complex (DVC).

The team says the DVC, which is part of the evolutionary ancient brainstem, controls a person’s food intake by making someone feel full after eating. Prior studies have shown that obesity blunts or eliminates the daily rhythms related to eating and the release of certain hormones. However, scientists haven’t been able to tell whether this is the cause or a side-effect of being overweight.

Fat changes the brain before changing the waistline

Dr. Lukasz Chrobok of Jagiellonian University in Poland worked with University of Bristol researchers to feed rats high-fat diets and observe its effect on the DVC. Study authors used two groups of animals, one eating a well-balanced diet with 10 percent of the calories coming from fat and one group eating a high-fat diet with 70 percent coming from fat.

To recreate the impact of an unhealthy diet on humans, the team started rats on this diet during adolescence (around four weeks-old for rats) and continued the meal plan for four straight weeks.

Results of the experiments show that, before the rats started to gain weight, the high-fat diet began to change the DVC’s daily neuronal rhythms. The neurons’ responses to regular appetite hormones also changed.

Translating the results to humans

Although human and mouse brainstems are similar, researchers note that their findings may not translate perfectly to people. Since rats are nocturnal animals, the peak of DVC activity occurs at the end of the day, which is a rest phase for rodents. In people, this is still an active phase for the brain.

Despite needing to conduct more crossover research, the team believes this may reveal a new way to combat obesity by restoring a person’s body clock after poor dieting.

“I’m really excited about this research because of the possibilities it opens up to tackle the growing health issue of obesity. We still do not know what are the time cues which are able to reset or synchronize the brainstem clock. Hopefully, the restoration of daily rhythms in this satiety center before or after the onset of obesity may provide new therapeutic opportunities,” says Dr. Chrobok in a media release by The Physiological Society.

In the United States, the CDC estimates that over 40 percent of the adult population is obese. Being overweight can lead to a number of other health conditions, including type 2 diabetes, heart disease, stroke, and some types of cancer.

The findings appear in The Journal of Physiology.

About Chris Melore

Chris Melore has been a writer, researcher, editor, and producer in the New York-area since 2006. He won a local Emmy award for his work in sports television in 2011.

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