According to a new study conducted by English and Polish researchers, high-fat diets wreak havoc with the biological clock (circadian rhythm), which may be one of the causes of obesity. The findings, reported in the Journal of Physiology, highlight the importance of circadian rhythms for good metabolic health and call for future testing of treatments that would restore the biological clock so people don’t eat too much.
This study comes at a time when obesity is rampant and the number of obese people in the world has almost tripled since 1975. In addition, obesity-related diseases are known to have been COVID-19 vulnerability factors, including type 2 diabetes, cancers, and cardiovascular diseases. By showing in animals how a high-fat diet disrupts the brain’s biological clock – which normally regulates satiety – and thus promotes obesity, this study suggests that resetting the clock is a prerequisite for maintaining or even regaining a healthy weight.
The biological clock in the brain regulates food intake
The biological clock has long been considered unique and is located in a part of the brain called the hypothalamus. However, recent research has shown that our body’s circadian rhythms (hormone levels, appetite, etc.) are also determined by various other parts of the brain and body. A group of neurons in the evolutionarily ancient brainstem called the dorsal vagal complex (DVC), is involved in producing a sense of satiety that helps with controlling food intake.
In obesity, the daily rhythms of food intake and the release of food-related hormones are distorted or shifted, according to the first results of a study carried out at the Jagiellonian University in Krakow in collaboration with researchers at the University of Bristol.
The study’s second finding is that high-fat diets appear to cause changes in the daily neuronal rhythms of the DVC and in the response of neurons that are specialized in controlling appetite-regulating hormones.
The study was conducted in two groups of young mice, one fed a balanced control diet and the other a high-fat diet (70% of the total calories consumed) for 4 weeks. Electrophysiological recordings were made to measure the evolution of neuronal activity in the dorsal vagal complex over 24 hours. The use of electrode arrays allowed simultaneous monitoring of approximately 100 neurons, evaluate the changes in neuronal activity and neuronal responses to metabolically relevant hormones for each dietary group. The experiment confirmed the following:
- A correlation between high-fat diets, circadian changes, and eventually the development of obesity.
- And in humans? Although human and murine cerebral trunks share common characteristics, mice are nocturnal. However, these data, as well as many previous studies, suggest that disturbances of the brain’s biological clock may contribute to obesity.
Opens new treatment avenues for obesity
Resetting the clock to combat obesity is a possibility according to lead author Dr. Lukasz Chrobok. He further suggests that the new research could open up new opportunities for obesity treatment. “We still don’t know what time cues can reset or synchronize the clock. But we believe that restoring the circadian rhythm before or after the onset of obesity could be a new treatment option.