It doesn’t take years for junk food to harm your health: a study shows that a diet high in ultra-processed foods reduces insulin sensitivity in the brain in less than a week.
Consumption of ultra-processed foods has been associated with numerous long-term health problems (1): overweight, obesity, mortality, cancers, etc. But are effects visible even after a short period?
Read: Ultra-processed foods linked to 32 harmful health effects
To find out, researchers at the University of Tübingen studied insulin sensitivity in the brains of healthy people temporarily subjected to a “junk food” diet. They became interested in insulin because of its involvement in different aspects of metabolic health.
Insulin is a hormone produced by the pancreas that tells cells to take in glucose when blood sugar levels are high. But his role does not stop there. “In the brain, insulin also signals the body to eat less by reducing food intake, explains Stephanie Kullmann, professor at the University of Tübingen (2). Improper fat distribution and continued weight gain are linked to the brain’s response to insulin. »
In a healthy person, insulin helps control appetite in the brain. But “In obese people, insulin loses its ability to regulate eating habits, leading to insulin resistance. » However, insulin resistance is associated with numerous pathologies, as Professor Ben Bikman demonstrates in his reference book, Insulin resistance.
Reduction of insulin sensitivity in 5 days
In this experiment, 29 normal-weight men, aged 19 to 27, spent 5 days eating 1,500 calories more of chips and candy bars (3). Insulin action in the brain was assessed by functional MRI combined with intranasal insulin administration.
Result: the participants’ insulin sensitivity dropped drastically in their brains. “Symptoms which, until now, have mainly been observed in obese people”comments Professor Kullman.
Even more worrying: even a week after returning to a normal diet, insulin sensitivity remained low in the brain. “Although no significant weight gain was observed, the short period was long enough for liver fat to increase significantly. »
This demonstrates that even short-term consumption of ultra-processed foods reduces insulin sensitivity in the brains of healthy people. “It appears that obesity is not just a matter of poor diet and lack of exerciseconcludes Stephanie Kullman. It also has a lot to do with adapting the brain’s insulin response to short-term diet changes, before any weight gain. »
How to combat insulin resistance
To avoid insulin resistance, it is advisable to limit the consumption of foods with a high glycemic index. But other lifestyle measures can also promote insulin sensitivity. For example, regular exercise would help restore the brain’s insulin sensitivity in overweight or obese people. Sleeping well and limiting stress also help fight insulin resistance.
