HQ Team
August 9, 2023: The brain’s hypothalamus gland is a relevant factor in obesity and little is known about how this region works in humans, researchers wrote in the peer-reviewed Neuroimage: Clinical journal.
Hypothalamus helps produce hormones that regulate heart rate, body temperature, hunger, and the sleep-wake cycle.
It controls hunger, thirst, and body temperature and regulates various activities in the body connected with metabolism, including the maintaining of water balance.
The hypothalamus also controls the action of the pituitary gland, a pea-sized gland situated at the bottom of the hypothalamus.
The researchers at the University of Cambridge revealed that the brain’s ‘appetite control centre’ is different in people who are overweight or living with obesity when compared to a normal healthy weight.
1,352 adults surveyed
The researchers 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 or BMI scores.
They looked for differences in the hypothalamus when comparing individuals who are underweight, healthy weight, overweight, and living with obesity.
“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,” said Dr Stephanie Brown from the Department of Psychiatry and Lucy Cavendish College, University of Cambridge.
“That’s because it is very small and hard to make out on traditional MRI brain scans.”
Evidence for the role of the hypothalamus in appetite regulation came from animal studies. “These show that there are complex interacting pathways within the hypothalamus, with different cell populations acting together to tell us when we are hungry or full.”
Larger volume
The University of Cambridge’s study found that the overall volume of the hypothalamus was larger in the overweight and obese groups of young adult humans.
The team found a significant relationship between volume of the hypothalamus and body mass index.
“These 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,” the researchers said.
The precise significance of the finding is unclear, including whether the structural changes are a cause or a consequence of the changes in body weight. 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.
Inflammation
In mice, just three days of a fat-rich diet is enough to cause this inflammation.
Other studies have shown that this inflammation can raise the threshold at which animals are full – in other words, they have to eat more food than usual 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 centre,” Dr Brown said.
“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 brain’s specialist immune cells, known as glia.
Heart disease, stroke
More research was needed to confirm whether increased volume in the hypothalamus was a result of being overweight or whether people with larger hypothalami were predisposed to eat more in the first place, according to the study.
More than 1.9 billion people worldwide are either overweight or obese. In the UK, according to the Office for Health Improvement & Disparities, almost two-thirds of adults are overweight or living with obesity.
This increases an individual’s risk of developing a number of health problems, including type 2 diabetes, heart disease, stroke, cancer, and poorer mental health.
