Junk food is addictive, and gorging on the guilty pleasure triggers the urge to binge eat, experts have warned.
Highly-calorific fast food floods the brain’s reward system with the feel-good chemical, dopamine.
The hormonal surge makes people want more and more.
In experiments feeding mice plenty of sweetened high-fat food for 24 hours increased the levels of dopamine in their brains, and led them to eat more.
But, when the hormone insulin with injected into the pleasure centre of their brains – a central area known as the ventral tegmental area – researchers noted a drop in appetite.
It’s believed the findings published in Proceedings of the National Academy of Sciences could also apply to humans – and could lead to a new way of combating the obesity epidemic.
Dr Stephanie Borgland, of Calgary University in Canada, said ‘in an environment rich with easily accessible, low-cost, palatable food, this plasticity may be a significant driver of overeating’.
She said: “These data indicate mice have increased food approach behaviours and consumption two days after the 24-hour access to the sugary and fatty food.”
Dopamine acts on regions of the brain that regulate movement, emotion, motivation and feelings of pleasure.
When activated at normal levels this system rewards our natural behaviours.
But overstimulating the system produces euphoric effects which produces an urge to repeat it.
Dr Borgland said: “In an environment with easy access to highly palatable and energy dense food, food-related cues drive food-seeking regardless of satiety – an effect that can lead to obesity.
“Priming effects of food-related advertising and consumption of palatable food can drive food intake.
“However, the mechanism by which this effect occurs, and whether these priming effects last days after consumption, is unknown.
“Here we demonstrate short-term consumption of palatable food can prime future food approach behaviours and food intake.”
But she said insulin – a hormone that controls blood sugar levels and helps you feel full after eating – can reduce food consumption.
Dr Borgland said: “Targeting this circuit with brain delivered insulin may provide a strategy to suppress food cravings.”
Previous research has shown fatty or sugary foods can be as addictive as cocaine.
Obese and compulsive eaters were irresistibly drawn to images of junk food in the same way cocaine addicts were when shown a bag of the white powder.
In the junk food eaters, the decision-making area of the brain – the orbit frontal cortex – released a surge of dopamine as they looked at high-fat foods.
This is the same reaction drug users get when presented with cocaine.
Another clue into how large quantities of fatty processed foods can change the way the brain is wired, lie with the results from a study on rats by the Research Institute in Jupiter, Florida.
When the treats were presented they began binge eating them – even though they had an unlimited supply of nutritional food.
The rats’ brain activity was measured and the study found that processed foods produced the same brain pattern that occurs with escalating intake of cocaine.
One-in-four adults in Britain is obese with levels more than trebling in the last 30 years. On current estimates over half the population could be obese by 2050.
Source: Daily Mail