The brain’s appetite “control center” is bigger in people who are overweight, according to new research.
Cambridge University scientists have shown that the hypothalamus — a key region of the brain involved in controlling hunger — is larger in the overweight and obese compared to people who are a healthy weight.
The research team says their findings add new evidence to the relevance of brain structure to weight and food consumption.
More than 1.9 billion people worldwide are either overweight or obese while almost two-thirds of adults are overweight or obese in the UK, according to official estimates.
Overweight people are at greater risk of developing serious health issues such as diabetes, heart disease and cancer.
Several factors influence how much we eat and the types of food we eat — including genetics, hormone regulation, and the environment in which we live.
The Cambridge team explained that what happens in our brains to tell us that we are hungry or full is not entirely clear, although studies have shown that the hypothalamus, a small region of the brain about the size of an almond, plays an important role.
Dr. Stephanie Brown, from Cambridge’s Department of Psychiatry, said: “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.”
She said most evidence for the role of the hypothalamus in appetite regulation comes from animal studies.
Those studies show that there are “complex” interacting pathways within the hypothalamus, with different cells acting together to tell us when we are hungry or full.
Dr. Brown and her colleagues used an algorithm developed using machine learning to analyze MRI brain scans taken from 1,351 young adults across a range of body mass index body mass index (BMI) scores, looking for differences in the hypothalamus when comparing those who are underweight, healthy weight, overweight and living with obesity.
The findings, published in the journal Neuroimage: Clinical, show that the overall volume of the hypothalamus was “significantly larger” in the overweight and obese groups of young adults.
The team also found a “significant” relationship between the volume of the hypothalamus and BMI.
Dr. Brown said the volume differences were most apparent in those sub-regions of the hypothalamus that control appetite through the release of hormones to balance hunger and fullness.
She says that while the precise significance of the finding is unclear, one possibility is that the change relates to inflammation.
Previous animal studies have shown that a high-fat diet can cause inflammation of the hypothalamus, which in turn prompts insulin resistance and obesity.
In mice, just three days of a fat-rich diet is enough to cause such inflammation.
Other research has shown that inflammation can raise the threshold at which animals are full – in other words, they have to eat more food than usual to feel full.
Study first author Dr. Brown added: “If what we see in mice is the case in people, then eating a high-fat diet could trigger inflammation of our appetite control centre.
“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.”
Study senior author Professor Paul Fletcher said: “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.”
He added: “Our hope is that by taking this new approach to analyze 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 says more research is needed to confirm whether increased volume in the hypothalamus is a result of being overweight or whether people with larger hypothalami are predisposed to eat more in the first place.
Produced in association with SWNS Talker
Edited by Arnab Nandy