The hypothalamus is an area of the brain that produces hormones that control body temperature, heart rate, moods, libido, sleep, thirst and the desire to eat. Scientists of the University of Cambridge, in the United Kingdom, discovered that this brain area is different in the overweight and obese people, compared to those at a healthy weight.
The researchers, who published the study in the journal Neuroimage: Clinical, stated that Their findings add up to more evidence to the relevance of brain structure for weight and food consumption. Being that, according to current estimates, more than 1,900 million people worldwide are overweight or obese.
The obesity disorder is one of the leading risk factors for numerous chronic diseases, including diabetes, cardiovascular disease, hypertension and stroke, as well as several types of cancer, according to the World Health Organization.
A large number of factors influence how much is consumed and the types of food you eat. Some of these are genetic predisposition, hormonal regulation, and the environment in which we live.
What happens in the human brain to indicate that it has hunger or that you are already satisfied is not entirely clear. But studies have already shown that the hypothalamus, a small region of the brain about the size of an almond, plays an important role.
The Cambridge researchers focused on further clarifying the question. Stephanie Brown, of the Department of Psychiatry and the Lucy Cavendish College of the University of Cambridge, the study’s first author, said: “Although we know that the hypothalamus is important in determining how much we eat, we actually have very little direct information about this brain region in living humans. This is because it is very small and difficult to distinguish in traditional MRIs.”
Most of the evidence for the role of the hypothalamus in appetite regulation comes from animal studies. This evidence shows that in the hypothalamus there are complex interaction pathways, with different cell populations acting together to indicate when the body is hungry or when it feels full.
Dr. Brown and her colleagues used an algorithm developed using machine learning to analyze brain MRIs taken from 1,351 young adults with varying body mass indexes. They looked for differences in the hypothalamus when comparing underweight, healthy weight, overweight and obese individuals.
Through the study published in Neuroimage: Clinical, the team found that the overall volume of the hypothalamus was significantly higher in the groups of overweight and obese young adults. In fact, the team found a relation significant among the Hypothalamus volume and the Body mass index.
These volume differences were most evident in subregions of the hypothalamus that control appetite by releasing hormones to balance hunger and satiety.
Although the exact meaning of the finding — including whether structural changes are a cause or a consequence of changes in body weight — is unclear, one possibility is that the change is related to inflammation.
Previous animal studies had shown that a High-fat diet can cause inflammation of the hypothalamus, which in turn leads to insulin resistance and obesity. In mice, three days of high-fat diet are enough to cause this inflammation.
Other studies have shown that this inflammation can raise the satiety threshold of animals, that is, they have to Eat more than usual to feel full.
Dr Brown commented: “If what we see in mice is the case in people, a high-fat diet could trigger inflammation of our appetite control centre. Over time, this would change our ability toWe know when we have eaten enough and how our body processes blood sugar, which would lead to weight “.
According to the team, inflammation could explain why the hypothalamus is larger in these people. One possibility is that the organism reacts to inflammation by increasing the size of immune cells specialized brain programs, called glia.
Meanwhile, the teacher Paul Fletcher, lead author of the study and a member of the Department of Psychiatry and Clare College, Cambridge, said: “The last two decades have provided us with important insights into appetite control and its possible alteration in obesity.
“Our hope is that, with this new approach to analyzing brain scans on large datasets, we can extend this work to humans and ultimately relate these subtle brain structural findings to changes in appetite and eating, and generate a more complete understanding of obesity,” Fletcher said.
The team acknowledged that more research is needed to confirm whether the increased volume of the hypothalamus is a consequence of being overweight, or whether people with larger hypothalamus are predisposed to eating more. It is also possible that these two factors interact with each other causing a feedback loop. Research with financial support from institutions such as: Bernard Wolfe Health Neuroscience Fund, Wellcome Trust, NIHR Cambridge Biomedical Research Centre, and Alzheimer’s Research UK.
