You might think you know a processed meal when you see one, but here’s some food for thought: nearly everything you can eat at the supermarket has undergone some kind of processing—such as washing, blanching, canning, drying or pasteurizing. In other words, if there is any change from the way the food began to the way it ends up on a shelf, it counts as processed.
But then there are ultraprocessed foods. Both frozen chopped spinach and canned sausages are processed, but the latter has undergone much more processing than the former. Ultraprocessed foods undergo an industrial process to move from farm to table. This often includes steps such as hydrogenation, which produces semisolid oils, and hydrolysis, which enhances flavors. These foods also have a variety of additives that help bind the ingredients together, increase their shelf life or make them more palatable.
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Some researchers hypothesize that certain foods are addictive. People don’t lose control over eating bananas, but with ultraprocessed foods, they show all the hallmarks of addiction, says Ashley Gearhardt, a professor of psychology and a nutritionist at the University of Michigan. Addictive drugs activate the striatal dopamine system—the brain’s pleasure center—by creating a dopamine spike followed by a rapid crash. “It’s like a quick hit that isn’t sustaining,” Gearhardt says. Ultraprocessed foods mimic nicotine and ethanol in the magnitude of that effect in the brain.
“That makes sense because the reward system of the brain was really shaped by the need to get calories,” Gearhardt says. The addictive agent in food could be one of many things, she says—taste, smell, sugar, fat and additives are all potential culprits. Studies in animals have shown that stopping the consumption of ultraprocessed foods—much like other addictive substances—elicits withdrawal symptoms such as anxiety and agitation.
