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Up until relatively recently, the scientific community scoffed at the idea of food addiction. It’s been thought that the act of overeating doesn’t really qualify as substance abuse. After all, drug addicts need increasing amounts of the stuff to get high, and they’ll show symptoms of withdrawal if they’re denied a fix. People who claim they’re a food addict, as in “addicted to pizza,” though, don’t experience pizza withdrawal. And most don’t necessarily need to ingest an increasing number of slices in order to get any enjoyment from it. But a recent study from Yale University* found that in some people, exposure to foods high in fat or sugar leads to chemical changes in the brain that make them want to return to those foods again and again.
In some ways, we’re all a bit predisposed to over-consumption. Our bodies are programmed to constantly search for food, and our brains are wired so that we’re rewarded when we find it. Humans evolved in a land of scarcity, not plenty, so having these drive and reward systems in place made sense when finding food meant survival.
Our ancient ancestors craved high-calorie foods and experienced pleasure from eating them, which then drove them to continue to seek them out. And it makes sense that sweet, fatty foods would be some of the most pleasurable—since they’re so calorie-dense, they would have been highly prized. Today, of course, we have plenty of food around at every turn. But our wiring hasn’t changed: the reward centers in our brains are made to ‘light up’ when we see, smell and devour our food.
The Yale researchers reported that high-tech brain scans helped them to distinguish so-called “food addicts” from ordinary, everyday over-eaters. Participants first filled out a food addiction questionnaire, then underwent a brain scan while admiring a picture of a milkshake. In those who had scored high on the questionnaire, just gazing at the milkshake caused their pleasure centers to light up like a Christmas tree.
It’s also been shown that when we eat foods high in fat or sugar, it drives up levels of dopamine—a neurochemical substance that stimulates the pleasure centers in the brain. But in some people, fatty, sugary foods don’t raise dopamine levels very much, so they crave more and more of these highly palatable foods in an attempt to do so.
It’s thought that this may be due, in part, to a shortage of dopamine receptors in the brain—areas where dopamine molecules first need to bind before they can work their magic. This same scarcity of receptors, or “reward deficit,” is also thought to lead to addictive behavior involving alcohol or drugs.
There’s no question that for many who struggle with their weight, the primary issue is that they have bad habits that need to be and can be changed. While the psychology of overeating has been pretty well-researched, food addiction studies are now delving into true physiological differences in the way people respond to food. This exciting new area of research may help to explain why some people are able to control their weight more easily—and why others feel completely powerless when it comes to controlling their urges to eat.
* Gearhardt AN, Yokum S, Orr PT, Stice E, Corbin WR, Brownell KD. Neural
Correlates of Food Addiction. Arch Gen Psychiatry. 2011 Apr 4. [Epub ahead of print]