Our Brains Have Evolved to Want High-Fat, High-Carb Foods

If you find donuts, pizza and cheeseburgers difficult to resist, your flimsy willpower isn't necessarily to blame as a study has found our brains are programmed to crave the double-whammy of carbohydrates and fats.

When we are faced with foods both high in fat and carbohydrates, like many processed foods are, the part of the brain in charge of processing reward is kicked into a higher gear when compared with foods high in one or the other, according to a team of researchers in the U.S., Germany, Switzerland, and Canada.

Scientists believe it all comes down to how we evolved to find food containing the highest amount of energy while being exposed to the least amount of danger.

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Scientists have investigated what makes pizza taste so delicious. Getty Images

When humans were hunter-gatherers, we mainly ate plants and animal meat and rarely encountered foods high in fat and carbohydrates, the authors of the study noted. And since farming methods developed around 12,000 years ago, it has become easier to produce fats and carbohydrates both separately and together. Only in the past 150 years have foods like donuts entered our diets, and our brains haven't yet evolved a new response.

To understand how the brain reacts to different foods, researchers scanned the brains of 206 adults while they were shown photographs of snacks high in either fat or sugar, or a combination of the two. The participants were also given money to bid on the foods they most wanted to eat.

The scientists found foods high in both carbs and fat awakened the neural circuits in the reward center of the brain, even more so than the foods they reported were their favorite. High-fat and high-carb foods also trumped foods that were sweeter or a larger portion size. What's more, subjects were willing to pay more for products high in both fat and carbohydrates.

Giving the example of a mouse who would not risk running into the open and exposing itself to a predator for low-energy food, Dana Small, director of Yale University's Modern Diet and Physiology Research Center, explained in a statement: "The biological process that regulates the association of foods with their nutritional value evolved to carefully define the value of a food so that organisms can make adaptive decisions."

"Foods containing fats and carbohydrates appear to signal their potential caloric loads to the brain via distinct mechanisms," she said. "Our study shows that when both nutrients are combined, the brain seems to overestimate the energetic value of the food."

The scientists hope their study published in the journal Cell Metabolism will contribute toward our understanding of the causes of obesity, why we eat when we aren't hungry and people's difficulties with weight loss and maintenance.