As per a recent study published in the journal Nature Metabolism, five days of indulging in sugary and junk foods can lead to brain activity patterns similar to those seen in people with obesity. A junk food splurge 'can shift brain patterns in healthy young men despite their body weight and composition remaining unchanged,' the study noted.
The authors of the study recruited 29 healthy male volunteers, of whom 18 went on a high-calorie diet (1,500-calorie packs of high-fat, high-sugar snacks) for five days, while the rest ate their normal diet during the same period. It was learnt, the authors note, "at the end of the five days, the junk-food group had higher activity than the control group in three brain regions involved in responses to dietary changes and rewards. This brain-activity pattern is similar to that seen in people with obesity or insulin resistance, which can lead to type 2 diabetes."
THE WEEK spoke to Dr Pradyut Ranjan Bhuyan, Consultant Neurologist, Manipal Hospital, Bhubaneshwar, who threw light on the effects of insulin in the brain. Excerpts...
Can bingeing on junk food alter brain activity?
Ans: Yes, junk food bingeing can modify brain activity in a pattern that is like drug addiction. Highly processed, high-sugar, high-salt, and high-fat foods activate the reward system of the brain, which releases dopamine, the "feel-good" neurotransmitter. As time passes, the brain loses sensitivity to dopamine, so individuals need more junk food to feel the same high. This is a process known as neuroadaptation, and it can make it more challenging to avoid junk food.
According to research, frequent bingeing on junk foods erodes self-control by harming the prefrontal cortex, the region responsible for decision-making and impulse control. It also sharpens brain circuits that promote desire, and the harder it is to fight overeating.
Please tell us in detail how insulin works inside our brain.
Insulin is not just for blood glucose regulation; insulin also exerts a dramatic influence on brain function. Inside the brain, insulin controls appetite, thinking, and memory. It binds to insulin receptors in areas like the hypothalamus, which dictates hunger. Normally, when insulin is functioning correctly, it deploys a signal of satiety, reducing hunger. But with insulin resistance (a frequent occurrence in obesity and diabetes), brain cells become resistant to insulin. This leads to greater hunger, binge eating, and difficulty in controlling body weight. Insulin also promotes brain health by increasing neuron survival and reducing inflammation. Defective insulin action in the brain has been linked to cognitive decline and Alzheimer's disease.
What actually happens inside the brain when one binges on junk food?
When you eat junk food, the reward mechanism in your brain is activated, releasing a flood of dopamine. This feels pleasurable, and you want more. Over time, the brain adapts to this by reducing the number of dopamine receptors, so you need more junk food to get the same feeling. The prefrontal cortex, which is in charge of self-control, becomes weaker, and you struggle more and more to resist cravings. Junk food also affects the hypothalamus, which regulates hunger, sending abnormal signals about when you're really full. The cycle increases overeating and can result in obesity, metabolic disease, and emotional eating.
Are brain patterns different in people who have obesity and who don't?
Brain function differs between those with obesity and those without obesity. Brain scan research shows that those with obesity are likely to have lower availability of dopamine receptors, and therefore may get less enjoyment from eating and need more food to feel satisfied.
The prefrontal cortex, responsible for decision-making and controlling impulses, may also be less active, so it is harder to resist unhealthy foods. The brain reward system is also hyper responsive to food visual cues and thus is also more responsive with increased craving. On the contrary, the low-obesity groups have enhanced control over impulse as well as better regulation over a response to food rewards, thereby being better capable of managing eating behaviour.
Is there a scientifically proven way in which we can train our mind to adapt to healthy eating and not tempt us into sugary, processed foods?
Repeated exposure is one of the ways in which frequently eating healthy foods rearranges taste preferences over a period of time. Mindful eating helps by sensitizing people to their fullness and hunger signals, reducing emotional eating. Cognitive behaviour therapy (CBT) reconditions thinking, helping to erase junk food addiction.
Dopamine fasting, or reducing sweet foods, re-calibrates the brain's reward system so healthier food becomes more rewarding. Exercise makes people more sensitive to dopamine as well, decreasing the appeal of unhealthy food rewards. In the long run, these measures make it possible for the brain to adapt, and it is easier to enjoy and sustain a healthy diet.
