Brain region for appetite control larger in obese population flags study, contributing to eating more

08 Aug 2023 --- Neuroscientists from different universities in Cambridge, UK, have unveiled a relationship between body mass index (BMI) and hypothalamus volume, the brain region controlling appetite control. A new study shows obese and overweight people have a larger volume than normal weight and slimmer people.

What and how much we eat is influenced by hormones, genetics and our environment. Prior studies claim that the almond-sized brain region, the hypothalamus, is essential in signaling whether we are hungry or full.

“Although we know the hypothalamus is important for determining how much we eat, we have very little direct information about this brain region in living humans. That’s because it is very small and hard to make out on traditional MRI brain scans,” says Dr. Stephanie Brown, lead author of the study and senior research associate at the University of Cambridge, UK. 

Fatty diets might also explain the larger size of the brain region, as it might expand as a response to inflammation.Potential feedback loop
The scientists used a machine learning-developed algorithm while analyzing MRI scans from 1,351 adults with various BMI scores. Although the findings are deemed “significantly unclear” as to whether or not it was a cause or effect of obesity, the hypothalamus volume was more extensive in the population with a higher BMI and especially in the regions controlling appetite.

The study, published in NeuroImage: Clinical, says that the changes might be explained by inflammation, as prior animal studies – where the primary scientific evidence comes from – show high-fat diets can potentially cause hypothalamus inflammation, driving insulin resistance and obesity. 

“If what we see in mice is the case in people, then eating a high-fat diet could trigger inflammation of our appetite control center. Over time, this would change our ability to tell when we’ve eaten enough and how our body processes blood sugar, leading us to put on weight,” says Brown. 

The authors argue that more research is needed to determine if the hypothalamus is more extensive as a response to obesity or if people eat more due to their hypothalamus being bigger. Additionally, they do not exclude the potential of the two factors interacting and causing a feedback loop. 

Inflammatory properties
Inflammation has been observed in mice after eating a high-fat diet for only three days and might also explain the larger size of the brain region, as it might expand as a response to inflammation.

“We hope that by taking this new approach to analyzing brain scans in large datasets, we can further extend this work into humans, ultimately relating these subtle structural brain findings to changes in appetite and eating and generating a more comprehensive understanding of obesity,” says Paul Fletcher, senior author of the study and professor at the Department of Psychiatry and Clare College, Cambridge, UK.

A recent Italy-based study found plant-based diets to be beneficial for obesity, Type 2 diabetes and hypertension compared to meat-based diets.

“Diets emphasizing the consumption of whole plant foods have also been associated with lower oxidative stress, inflammation, better endothelial function and increased insulin sensitivity,” Nicoletta Pellegrini, co-author of the study and associate professor in Human Nutrition at the Department of Agricultural, Food, Environmental and Animal Sciences at the University of Udine, Italy, previously told Nutrition Insight.

Edited by Beatrice Wihlander