Link between brain size and obesity in adolescents

The size of the brain’s pleasure and reward processing sensors could be behind increased body fat in adolescents and obesity later in life, new research has found.

ACU researchers Karen Caeyenberghs from the Mary MacKillop Institute for Health Research and Valentina Lorenzetti from the School of Behavioural and Health Sciences were part of a major study into obesity and its links to the brain.

Published in Nature Scientific Reports, the study showed a strong link between body fat and size of the nucleus accumbens– also known as the pleasure centre of the brain – in adolescents.

Researchers also found body fat is linked to the size of the medial orbitofrontal cortex — a region at the front of the brain that is involved in reward processing of food cues.

Led by Dr Naomi Kakoschke from the Monash Institute of Cognitive and Clinical Neurosciences, this is one of the first studies to examine the link between excess body fat and brain health in adolescents and adults.

Associate Professor Caeyenberghs said as our brains become used to high rewards from impulsivity – the tendency to act on a whim without consideration of the consequences – body fat acquired from adolescence could develop into obesity with age due to a lack of behavioural change.

“We know that both reward-based learning and executive control are compromised in people who are overweight or obese. People with excess weight show heightened responsivity to highly palatable food cues, such as television commercials for food, and less ability to control those unhealthy urges,” she said.

She said the research may help us understand why for, some people, it is harder to lose and keep weight off.

The study examined the association between body fat, impulsivity and brain structure in 127 people across the body mass index spectrum.

“We know that excessive body fat accumulation increases the risk of developing chronic health conditions including cardiovascular disease, type 2 diabetes and dementia, but we need to look at how the workings of our brain play a part in this body fat gain,” Dr Kakoschke said.

“Studies have repeatedly shown that reward sensitivity is elevated in people with obesity, particularly for those with binge eating disorder. We hope future studies can point to brain health as being a more accurate indicator of body composition and body fat than BMI.”

Two in three Australians are considered overweight or obese and Australia is the fifth most obese nation in the world, according to the OECD.

One in four Australian children aged 2-17 were considered overweight or obese in Australia.

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