Size of brain’s ‘appetite control center’ may explain why certain people become obese

CAMBRIDGE, United Kingdom — Could the key to understanding obesity be the size of a person’s brain? A new study has found that the brain’s “control center” for appetite is larger in individuals who are overweight.

Scientists at the University of Cambridge have discovered that the hypothalamus — a key region of the brain involved in controlling hunger — is more substantial in overweight and obese people than in those with a healthier weight. This finding provides new evidence connecting brain structure to weight and food consumption, according to the research team.

Globally, more than 1.9 billion people are classified as overweight or obese. More than four in 10 American adults are obese, according to the CDC. Being overweight increases the risk of developing serious health problems such as diabetes, heart disease, and cancer.

Several factors influence our eating habits and food choices, including genetics, hormone regulation, and our living environment. The Cambridge team acknowledges that the brain’s mechanisms to signal hunger or fullness remain unclear. Still, studies have indicated that the hypothalamus, a brain region the size of an almond, plays a crucial role.

“Although we know the hypothalamus is important for determining how much we eat, we actually 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 from the Department of Psychiatry and Lucy Cavendish College, University of Cambridge, in a media release.

Sugar and junk food surrounding a brain
(Photo by Per Bengtsson on Shutterstock)

Dr. Brown stated that most evidence regarding the hypothalamus’s role in appetite regulation derives from animal studies. These studies have demonstrated complex, interacting pathways within the hypothalamus, with various cells coordinating to signal hunger or fullness.

The researchers employed a machine-learning algorithm to analyze MRI brain scans of 1,351 young adults with varying body mass index (BMI) scores. They looked for differences in the hypothalamus among individuals who are underweight, of healthy weight, overweight, or living with obesity.

Published in the journal Neuroimage Clinical, their findings revealed that the overall volume of the hypothalamus was “significantly larger” in overweight and obese young adults. There was also a “significant” correlation between the volume of the hypothalamus and BMI.

Dr. Brown noted that the most pronounced volume differences were found in the hypothalamic sub-regions controlling appetite through hormone release to regulate hunger and fullness.

While the exact significance of this finding remains unclear, Dr. Brown posited that the change might be related to inflammation. Previous animal studies have shown that a high-fat diet could cause inflammation in the hypothalamus, leading to insulin resistance and obesity.

In mice, inflammation can occur within just three days of consuming a fat-rich diet. Other research has demonstrated that this inflammation can increase the amount of food required to feel full.

“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 to how our body processes blood sugar, leading us to put on weight,” Dr. Brown continues.

“The last two decades have given us important insights about appetite control and how it may be altered in obesity. Metabolic researchers at Cambridge have played a leading role in this,” adds Professor Paul Fletcher, the study’s senior author, from the Department of Psychiatry and Clare College in Cambridge.

“Our hope is 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.”

The Cambridge team concludes that further studies are still necessary to determine whether an increased volume in the hypothalamus results from being overweight or if individuals with larger hypothalami are predisposed to eat more in the first place.

South West News Service writer Stephen Beech contributed to this report.

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