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Why Does Pizza Seem Addictive?

Peptides in cheese can act on the brain and lead to a feeling of calm.

Key points

  • Cheese contains a protein that releases an opiate during digestion.
  • Animal and brain imaging studies support the idea that some foods may have addictive properties.
  • Avoiding temptation can help people change their eating habits.

It’s hard to stop at one potato chip or pizza slice; no one doubts that. Recent research aims to explain why.

In one study, when researchers led by Ashley Gearhardt, a clinical psychologist at the University of Michigan, asked 500 people to report how they consumed each of 35 foods, pizza turned out to lead to the most addictive-like eating behavior. (Food addiction is not a psychiatric diagnosis in the DSM-5, but the term was used in the research.)

Pizza packs a double whammy: The crust is made of refined white flour that quickly turns into glucose in your bloodstream, and the cheese contains casein, a protein that releases casomorphins during digestion, a kind of opiate.

What makes cheese addictive?

First, let’s consider the crust. Chewing a leaf of the coca plant isn’t likely to turn you into an "addict"; cocaine has been engineered so that the most addictive substance in the plant moves quickly through your bloodstream. In the same way, addictive foods funnel glucose in refined carbohydrates quickly into the bloodstream. After all, the food industry’s goal is to make you eat, and buy, more of their products, not to make you content with a small portion. Fat helps the process along. This is why we love products that combine flour and fat, like cookies, cakes — and pizza.

Now add the casomorphin-producing cheese. “Casomorphins attach to the brain’s opiate receptors to cause a calming effect in much the same way heroin and morphine do," writes Neal Barnard, MD, author of the book Breaking the Food Seduction: The Hidden Reasons Behind Food Cravings — And 7 Steps to End Them Naturally.

According to the National Institutes of Health Dairy guidelines, you should aim to eat no more than 1.5 ounces of cheese a day. Any more than a couple of slices of pizza would be over the limit. But especially if you’re anxious, you may crave more and more of that calming effect. Interestingly, in this study, men reported more problems with overeating cheese (and also steak) than women.

Brain imaging studies have supported the idea that people who eat a great deal of junk food, for instance, ice cream, can develop tolerance — just like you might with a drug. So you end up needing more of the food to satisfy your craving.

A good deal of evidence on the similarity between compulsive food and drug consumption comes from studies with rats. Rats are more likely to binge eat Oreo cookies or frosting than their typical chow; and if you feed them cheesecake, their brains start to look like the brains of drug-addicted rats. If you feed rats sugar and then take it away, they go into a state that looks like opiate withdrawal; their teeth chatter and they become aggressive.

Another sign of addiction: even when researchers punish rats with shocks to the feet, the rats keep lunging toward highly processed foods. This may be similar to the alcoholic who keeps drinking even after he loses his job or wife.

After pizza, chocolate, chips, cookies, ice cream, French fries, cheeseburgers, soda, and cake are the most addictive foods — followed by cheese in tenth place.

Many vegetarians love cheese. If you decide to cut back, or cut out, cheese, you may rediscover the wonderful flavors of broccoli and other vegetables that you used to hide under cheese. Try substituting avocado on sandwiches or in salad, and nuts or nut butters. Both contain healthy fats. You can also try vegan cheese made from soy or nuts.

It may take effort. In other research, Dr. Gearhardt’s team has concluded that cutting back on highly processed foods can trigger symptoms of withdrawal in humans — irritability, fatigue, sadness and cravings. Although you may know a food isn’t good for you, quitting is a struggle. Dr. Gearhardt’s patients “have typically tried dozens of strategies like crash diets and cleanses to try and get their relationship with these foods under control,” she said in The New York Times. “While these attempts might work for a short time, they almost always end up relapsing.”

Cheese doesn’t, however, cause an altered mental state in the way that alcohol or cocaine do. It may be that you can switch easily from one food to another. But patterns of overeating can still end up leaving you feeling out of control.

So what can you do? Don’t underestimate one of the common-sense methods of managing your eating: Remove temptation. If cheese or pizza is a problem, don't keep it in your home, bring chili to a regular pizza gathering, and avoid driving by a favorite pizza shop.

Another strategy is to create a ritual around eating, perhaps prayer. Cut up your food before eating. it. Rituals seem to enhance self-control and also slow down eating. If you do decide to have a slice, what if you cut it up on a plate rather than holding it in your hand?

A version of this story also appears on Your Care Everywhere.

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