Yes, that donut is delicious–practically irresistible. And here’s why. Yale researchers have found that foods that combine fat and carbohydrates create a powerful reward in the brain, reports USA Today. The investigators recruited 206 volunteers and gave them a small amount of money to bid on various foods in an auction-like way, while having their brain scanned in real time. The team found that the participants were more likely to pay for foods containing the fat-carbo combination, and moreover, the brain scan reflected stimulation in an area associated with reward. Ironically, foods containing the magic fat-carbo combo don’t exist in nature, except for breast milk, which contains 3.5% fat and 7% carbohydrates. Snack food, by comparison, is typically about one quarter fat and half carbohydrates. The results at least partly explain rising rates of obesity.
It turns out that combining fat and carbs created a craving that went beyond “two plus two”; the combination generated a unique response that was greater than the sum of the parts. The study, says Yale psychiatrist and senior author Dana Small, is one of the first to show that "our modern foods, processed foods, are different. They are affecting our physiology differently," per NBC. The volunteers were also asked to guess how many calories were in the various foods. According to Small, they were good at estimating calories from fatty food, but bad at carbohydrates. The bottom line? As YaleNews reports, the human body has not evolved to handle snack food like “donuts, French fries, chocolate bars, and potato chips,” says Small, and its reward system “may backfire to promote overeating and obesity.” (Read more pizza stories.)