Scientists reveal the neurobiological basis of obesity

According to a new study published in The Journal of Physiology, a high fat diet fed to rats disturbs their brainstem body clock. Since this clock is essential for controlling satiety, such disturbances generally lead to over-eating and obesity.

The number of obese people has tripled worldwide since 1975. In England alone, 28 percent of adults are obese and over 36 percent are overweight. Obesity is known to lead to other health problems such as cardiovascular disease, type 2 diabetes, strokes, and several types of cancers.

Until recently, scientists thought that the master body clock was located solely in the brain area called the hypothalamus. However, further research has shown that other parts of the brain and body also control our body’s daily rhythms, including hormone levels, appetite, and satiety markers. Specifically, the dorsal vagal complex (DVC), a cluster of neurons in the evolutionary ancient brainstem, has been found to control food intake by inducing a feeling of satiety.

Although it was known that, in obesity, daily rhythms in food intake and the modulation of eating-related hormones are blunted or eliminated, it has not been clear whether these disturbances in the brain areas controlling appetite are a cause or result of obesity.

Researchers from the Jagiellonian University in Krakow and the University of Bristol found that rats fed with a high-fat diet showed significant changes in the DVC’s daily neuronal activities and responses to metabolically-relevant hormones, even before the rats began gaining weight. Thus, it appears that disturbances in the DVC’s timekeeping induced by high fat diets are important causes of obesity, rather than a result of excessive weight. 

Although more research is needed in order to understand whether these processes are similar in the case of humans, this study is one of the first to discover a neurobiological basis of obesity, and thus to open important therapeutic pathways.

“I’m really excited about this research because of the possibilities it opens up to tackle the growing health issue of obesity,” said study first author Dr Lukasz Chrobok. “We still do not know what are the time cues which are able to reset or synchronise the brainstem clock. Hopefully, the restoration of daily rhythms in this satiety centre before or after the onset of obesity may provide new therapeutic opportunities.”

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By Andrei Ionescu, Earth.com Staff Writer