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Link found between body fat and pleasure sensors in our brains

The size of the brain’s pleasure and reward processing sensors could be influencing increased body fat in adolescents, and potentially obesity later in life, according to new research.

Study results from Monash University have shown that there is a “strong link” between body fat and size of the nucleus accumbens (NAcc) — also known as the “pleasure centre” of the brain — in adolescents.

Researchers examined the association between body fat (an index of weight severity), impulsivity (a vulnerability factor for obesity) and brain structure in 127 people across the body mass index (BMI) spectrum. It also provides initial evidence of the link between BMI and NAcc volumes among adolescents using body fat as an indicator of obesity.

The study, undertaken by Monash Institute of Cognitive and Clinical Neurosciences and led by Dr Naomi Kakoschke, is one of the first global studies to examine the link between excess body fat and brain health in adolescents and adults.

Findings showed that body fat was up to 3 per cent higher in adolescents who had a larger left NAcc than similar people in their age bracket, the researchers noted, with the volume of an individual’s left medial orbitofrontal cortex (OFC) also found to be positively associated with an increase in body fat due to the role it plays in reward and emotion processing.

An individual’s body fat percentage was also found to correlate with the size of their medial orbitofrontal cortex, which is a region at the front of the brain that is involved in reward processing of food cues.

“As our brains become accustomed to the 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,” the researchers said.

“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,” Dr Kakoschke said.

Previous research in children, the researchers mused, demonstrated that responsivity to food advertisements and higher NAcc volume are associated with genetic risk for obesity and higher body fat composition.

“This also supports the early formation of unhealthy eating behaviours due to a combination of enhanced reward-related sensitivity in the striatum and impulsivity-related alterations in the structure of the prefrontal cortex,” they surmised.

“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.”