Obesity may trigger inflammation that damages the brain, research suggests.
Scientists from the University of São Paulo compared the brain scans of 59 obese teenagers and 61 adolescents of a healthy weight.
Among the heavier participants, they found reduced white matter in the corpus callosum, a bundle of nerves that connects the left and right side of the brain.
In simple terms, grey matter contains the bulk of our nerve cells, while white matter is made up of long filaments that transmit electrical signals between neurones.
This damage is reportedly linked to the inflammatory hormone leptin, which is made by fat cells and helps regulate appetite.
Obesity is a growing problem, with one in three children in the UK being overweight or obese by the time they leave primary school, Public Health England statistics show.
In 2017/18, 335 16-to-24 year olds in England alone were admitted to hospital with a “primary diagnosis of obesity”, according to NHS Digital.
And in the US, one in five (20.6%) of 12-to-19 year olds are obese, data from the Centers for Disease Control and Prevention reveals.
Obesity is known to cause inflammation, which has been linked to everything from heart disease to cancer.
To learn more about how it affects the brain, the scientists analysed scans for “fractional anisotropy” (FA). A reduction in FA indicates white matter damage, they claim.
The scans show reduced FA in the obese participant’s corpus callosum, as well as their middle orbitofrontal gyrus. This is the brain’s “reward centre” and has been linked to emotional control.
Results will be presented in full at the Radiological Society of North America conference in Chicago next week.
Past research suggests obese people’s brains do not respond to leptin, which may cause them to overeat.
“Brain changes were found in obese adolescents related to regions responsible for control of appetite, emotions and cognitive functions,” study author Dr Pamela Bertolazzi said.
The study also found the overweight participants had altered levels of insulin, which helps the body use glucose for energy.
Carrying too much weight has been associated with insulin resistance. This occurs when the body stops responding to the hormone and can lead to type 2 diabetes.
“Our maps showed a positive correlation between brain changes and hormones, such as leptin and insulin,” Dr Bertolazzi said.
“In the future, we would like to repeat brain MRI in these adolescents after multi-professional treatment for weight loss to assess if the brain changes are reversible.”