A key region of the brain involved in controlling appetite is different in people who are overweight from individuals of a healthy weight, scientists report today.
The study, published by a team from the University of Cambridge, UK, adds further evidence to the relevance of brain structure to weight and food consumption, write the authors in Neuroimage: Clinical.
Dr Stephanie Brown, from the Department of Psychiatry and Lucy Cavendish College, 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.”
Most of the evidence for the role of the hypothalamus in appetite regulation comes from animal studies, which show complex interacting pathways within the hypothalamus, with different cell populations acting together to tell us when we are hungry or full.
Study first author Dr Brown and colleagues used an algorithm to analyse MRI brain scans taken from 1,351 young adults across a range of BMI scores, who were underweight, healthy weight, overweight and living with obesity.
They found the overall volume of the hypothalamus was significantly larger in the overweight and obese groups of young adults, with a significant relationship between volume of the hypothalamus and body-mass index (BMI).
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.
They believe it is possible the change relates to inflammation. Previous animal studies have shown a high fat diet can cause inflammation of the hypothalamus, which in turn prompts insulin resistance and obesity.
Other studies have shown this inflammation can raise the threshold at which animals are full.
Dr Brown said: “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.”
One suggestion is that the body reacts to inflammation by increasing the size of the glia, the brain’s specialist immune cells, but they add more research is needed.
Brown SSG et al. Hypothalamic volume is associated with body mass index. Neuroimage: Clinical 8 August 2023; doi: 10.1016/j.nicl.2023.103478
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