French fries, cream cakes, french fries and chocolate bars make you fat and unhealthy. Still, we can’t keep our hands off it. Scientists at the Max Planck Institute for Metabolism Research in Cologne have now found an explanation for this: foods that are rich in fats and carbohydrates have a particularly strong influence on the reward system in our brain.
Both fatty and high-carbohydrate foods activate the reward system in the brain, but via different signaling pathways. When carbohydrates and fats come together in food, this effect is amplified. In nature there are no foods that are high in fats and carbohydrates: they are either rich in fats, such as nuts, or rich in carbohydrates, such as potatoes or grains.
Breast milk is an exception. “All mammals know breast milk,” says the head of the research group, Marc Tittgemeyer from the Max Planck Institute for Metabolic Research, who carried out the study in collaboration with researchers from Yale University in Connecticut. “We are likely to be influenced by breast milk to react intensely to high-carbohydrate and high-fat foods and to find this particularly rewarding as it is of vital importance.”
The scientists wanted to know whether people prefer foods with different sources of calories. To answer this question, 40 volunteers played a food computer. The foods on offer were high in fat, carbohydrates, or both. In order to earn it, the test subjects had to outbid the computer and thus check their willingness to pay. Most of the money was offered for high-fat and high-carbohydrate foods, suggesting that it appeared to be the most attractive to study participants.
While they were playing, the researchers recorded the subjects’ brain activity using magnetic resonance imaging. The measurements showed that a combination of fats and carbohydrates activated the brain areas of the reward system more intensely than the other foods on offer. This finding is consistent with the results of the game.
The reward signal is stronger than the feeling of satiety
A reward that has contributed to human survival through evolution is destroying us in today’s world of abundance. “We shouldn’t always say no. That’s why we usually don’t stop eating even though we’re full, ”emphasizes Tittgemeyer. Obviously, the reward signals overshadow satiety – oversaturation and obesity are the consequences.
In addition, estimating the nutritional value of high-fat and high-carbohydrate foods is difficult: when the study participants were asked to estimate the calorie content of the presented food, they managed to identify the high-fat or high-carbohydrate food with relative accuracy. In contrast, they have often been wrong about foods high in fat and carbohydrates. However, these types of foods do not automatically produce more calories.
The results could play an important role in the treatment of obese people. In particular, when food becomes an addictive factor, the treatment of consumer behavior is of great importance and a fundamental step out of addiction.
Publication: Alexandra G. DiFeliceantonio et al., “Supraadditive Effects of Combination of Fat and Carbohydrates on Food Rewards”, Cell Metabolism, 2018; doi: 10.1016 / j.cmet.2018.05.018