A new study out of Yale seems to have uncovered why some people continue to eat their way toward obesity even when they know the foods they eat and the amounts of which they eat it pack on the pounds and clog our arteries. It’s because eating a combination of fats and carbs signals our brains to go haywire similarly to drug use and abuse. Fats and Carbs are our brains on crack.

The Study

Dana Small, executive of Yale University’s Modern Diet and Physiology Research Center and her researchers took 206 adult subjects and had them undergo brains scans while being shown photographs of snacks containing mostly fat. Then they showed them pictures of foods that contained mostly sugar. The third group of photos were foods that contained combinations of both fats and carbohydrates – processed foods like pasta, pizza, and burgers that comprise most of the American diet. The volunteers were each given a small amount of money — under $10 — to “bid” on snack items shown. They also asked their volunteers to pick their favorite foods from this list of 39 foods.

Their results were published last week in the journal, Cell Metabolism, and showed that foods that combined fat and processed carbohydrates stimulated the brain even when people claimed they did not particularly like that food more than others. “Foods that combined carbohydrates and fats generated a response much greater than the sum of the parts,” Small said. “It’s one of the first studies to show that our modern foods, processed foods, are different. They are affecting our physiology differently.”

But why?

The evolution of food

Combining fat and carbs may overstimulate the brain’s reward mechanism much in the same way as drugs of abuse do, the researchers said. But it’s not a conscious response because most of us know these foods, especially when eaten in large amounts, are not healthy. And it’s not pleasure. So what it is? According to Small, it’s an unconscious signal that highjacks our body’s inborn signals governing food consumption and causes it to go haywire.

The researchers noted that our hunter-gatherer ancestors ate mostly woody plants and animal meat. “In nature, foods high in fat and carbohydrate are very rare and tend to have fiber, which slows metabolism,” Small says. “By contrast, it is very common for processed foods to have high fat and high carbohydrate loads.”

“After the domestication of plants and animals and the development of grain and dairy production around 12,000 years ago, opportunities to consume fat and carbohydrates together increased, but processed foods like donuts, which could contain 11 grams of fat and 17 grams of carbohydrate, have only been around for 150 years, not long enough for us to evolve a new brain response to them.”

The researchers theorized that the combination of fats and carbohydrates signals pathways that creates an effect which human physiology has not yet evolved to handle. Consistent with this suggestion, rodents given access to fat alone or carbohydrate alone regulate their total daily caloric intake and body weight. But given unrestricted access to fat and carbohydrates, they are more attracted to that combination and quickly gain weight. In this instance, people are no different.


1. Foods combining fats and carbohydrates more rewarding than foods with just fats or carbs. Science Daily.