Why our brains prefer fatty, high-sugar foods

Do you constantly wonder why you are addicted to the highest calorie foods when the sight of a cucumber gives you no pleasure? Look no further, it’s the fault of your neurons and the neural circuits they constitute in the brain.

According to a study published Thursday, June 14 in the newspaper Cell Metabolism, the reward system in our brain much prefers foods high in fat and carbohydrates.

A study of brain reactions

Professor Dana Small, director of the Yale Physiological Research Center as well as Swiss, German, and Canadian colleagues, wanted to understand which brain mechanisms explain the genetic predispositions for obesity, the habit of eating without being hungry or difficulty losing weight. They then subjected participants to brain scans while showing them photos of snacks combining fat and sugar or fat and carbohydrates.

Result of the experiment: the subjects were willing to pay more for foods high in fat and carbohydrates. What’s more, the researchers noted that this food combination ignites more neural circuits in the brain’s compensation system than a preferred and potentially sweeter, more energy-dense food or larger portion of food.

A particular valuation of food

“The biological process that regulates the association of foods with their nutritional value has evolved to define the value of a food so that organisms can make appropriate decisions,” says Dana Small. “For example, a mouse is not going to take the risk of exposure to a predator if the food provides little energy “, she specifies.

Surprisingly, foods containing fat and carbohydrates seem to signal their potential calorie intake via separate brain mechanisms. Our participants were very good at estimating calories from fatty foods and much less at estimating calories high in carbohydrates. Our study shows that when the two are combined, the brain tends to overestimate the energy value of a food, ”she continues. According to her, carbohydrates release dopamine in the brain through a metabolic signal still unknown to scientists.

Our brains didn’t have time to adapt to ultra-processed foods

Our hunting ancestors ate mostly plants and animal meat, the researchers say in their study. “In nature, foods high in fat and carbohydrates are very rare and tend to have fiber, which slows down the metabolism,” explains Dana Small.

But, after the domestication of plants and animals and the development of agriculture around 12,000 years ago, we have become more accustomed to consuming fat and carbohydrates together. However, processed foods like donuts, which contain 11 grams of fat and 17 grams of carbohydrates, only appeared 150 years ago. Thus, our brain has not had time to evolve enough to adapt its response to this kind of little taste pleasures.

This is why the rodents that Dana Small and her colleagues gave unrestricted access to foods high in fat and carbohydrates grew very quickly.

Therefore, while waiting for the human brain to find a solution to adapt to the ultra processed food (it is not only found in junk food but also a lot in the dietetic shelves of the supermarket), it would seem wiser to avoid it as much as possible and to favor foods directly obtained from plants or animals. Even if it means feeling less rewarded …