Is the secret to slimness in your head? Brain structure of overweight people differs from the one of slim people

Why the hypothalamus of overweight people differs from the one of slim people. Cambridge scientists

"Got an appetite? Look at the cellulite!", nutritionists and fitness trainers joke. According to the latest WHO figures, more than 1.9 billion people worldwide are either overweight or obese. Food has become too plentiful and we have learned to recognize the brain signals that control appetite," scientists explain.

Researchers at the University of Cambridge in the course of scientific experiments have found out: the "appetite control center" of the brain in overweight and obese people is different from the one of slim people. Is the secret of slimness in the head? How does the brain influence our eating habits?

Is there a connection between the brain and weight?

Everything is in our hands, or rather in our heads, scientists prove.

Cambridge researchers have shown a fatal link between brain structure and food intake. The hypothalamus, an important part of the brain that controls appetite, is significantly different in overweight and obese people compared to people of a healthy weight.

Many factors influence what and how much we eat, starting from genetics and hormonal background to traditions in society. What processes occur in our brain when we are hungry or satiated? Research shows: a small almond-sized area of the brain called the hypothalamus plays a key role.

"We know that it is the hypothalamus that determines how much we eat, but we have very little information about this area of the brain in living people. It's too small to be seen on traditional MRI brain scans," says Dr. Stephanie Brown of the Department of Psychiatry at the University of Cambridge.

This is why most of the evidence for the hypothalamus' role in appetite regulation comes from animal studies. They show that there are complex interacting mechanisms in the hypothalamus that tell us when we are hungry or satiated.

Why does the hypothalamus increase in volume?

Despite the difficulty of studying the hypothalamus, scientists decided to study this part of the brain in humans. Dr. Brown and his colleagues studied MRI brain scans of 1,351 people with different body mass indexes using computer technology. Comparing data from underweight, healthy and overweight people, scientists found differences in the hypothalamus of obese subjects.

The team found that the total hypothalamic volume was significantly larger in the group of overweight and obese young adults in a study published in the Neuroimage: Clinical scientific journal. The researchers found a link between hypothalamic volume and body mass index.

The differences in brain volume concerned those points in the hypothalamus that control appetite, promoting the production of hormones that balance hunger and satiety.

What influences the change in brain structure?

Scientists don't fully know whether the cause of structural changes in the brain is related to weight gain or inflammation. Previous animal studies have shown that a high-fat diet can cause inflammation in the hypothalamus, which in turn causes insulin resistance and obesity.

Mice need three days of a high-fat diet only to cause hypothalamic inflammation. Other studies have shown that this inflammation can raise the animals' satiety threshold: they have to eat more food than usual to feel satiated.

Study author Dr. Brown comments, "If what we observe in mice is also happening in humans, eating fatty foods may cause inflammation of our appetite control center. Over time, this alters our ability to detect feelings of satiety, which leads to weight gain."

The inflammation may explain why the hypothalamus of obese people is larger than that of normal-weight people, the scientists said. Paul Fletcher, Professor in the Department of Psychiatry at Clare College, Cambridge, believes the study provides important information about the true causes of overweight and obesity:

"We hope that by taking a new approach to analyzing brain scans in large datasets, we can link these subtle structural changes in the brain to changes in appetite and create a complete understanding of obesity."

Is increased brain volume the result of being overweight or are people with a larger hypothalamus predisposed to eat more in the first place? Researchers do not have exact answers to this question yet. They assume that these two factors interact with each other, causing a feedback loop.