New Research Challenges the ‘Body Knows What It Needs’ Theory and Where Men Differ From Women.
A cupcake is calling you.
You can practically taste the sweet, creamy goodness. You want it so badly you can’t think of anything else. But is it really the taste you crave—or the pleasant associations it brings? Or do you crave it partly because you know you shouldn’t have it? Will fighting the urge make it go away or only make it worse?
Why do people crave certain foods at certain times? There’s a surge of research in this field as scientists try to understand the complex relationships among food, mood, and behavior.
Scientists are exploring all these questions as they seek to understand food cravings. The research is taking on new urgency with the nation’s obesity epidemic, since cravings are widely believed to influence snacking behavior, binge eating and bulimia.
Among the findings so far:
Food cravings activate the same reward circuits in the brain as cravings for drugs or alcohol, according to functional MRI scans, tests that measure brain activity by detecting changes in blood flow.
Nearly everyone has food cravings occasionally, but women report having them more often than men, and younger people crave sweets more than older people do.
In one study, 85% of men said they found giving in to food craving satisfying; of women, only 57% said they did.
While many women report craving salt, fat or bizarre combinations of food during pregnancy, researchers can’t find much scientific validation. They suspect folklore and the power of suggestion instead.
What We Crave
For decades, researchers surmised that food cravings were the body’s subconscious effort to correct nutritional deficiencies. Longing for steak could indicate a need for protein or iron, according to this theory. Chocoholics might be low on magnesium or other mood-altering chemicals that chocolate contains, including phenylethylamine, a compound humans produce when they’re in love.
But a growing body of research casts doubt on the nutritional-deficiency notion. After all, few people crave vitamin-rich green leafy vegetables and many other foods contain more phenylalanine than chocolate—including salami and cheddar cheese.
Instead, studies show that food cravings involve a complex mix of social, cultural and psychological factors, heavily influenced by environmental cues. While chocolate is consistently the most-craved food in North America, Japanese women are more likely to crave sushi, a recent study found. And only 1% of young Egyptian men and 6% of young Egyptian women reported craving chocolate, according to a 2003 survey. “Many other languages don’t have a word for ‘craving.’ The concept seems to be uniquely important in American culture,” says psychologist Julia Hormes at the University at Albany.
In the U.S., about 50% of women who crave chocolate say their cravings peak around the onset of their monthly period. But researchers haven’t found any correlation between food cravings and hormone levels, and postmenopausal women don’t report a big drop in chocolate cravings, a 2009 survey found. Some psychologists suspect that women may be “self-medicating,” because sweets and carbohydrates spur release of serotonin and other feel-good brain chemicals.
A study of 98 female students at the University of Pennsylvania last year found that those who reported the most cycle-related cravings also had a history of dieting, eating disorders and high body mass indexes. “These seem to be women who think, ‘I shouldn’t have any chocolate at all,’ but then they give in and have the whole bar,” says Dr. Hormes, who led much of the U. Penn research. “The more they try to restrict it, the more they craved it.”
Typically, people crave foods they enjoy—but not always. “It’s possible to like a food without craving it, and crave a food without liking it,” says Marcia Pelchat, a food psychologist at the Monell Chemical Senses Center, a research facility in Philadelphia.
Too many sweets can flood the brain’s reward circuits, causing constant cravings.
In one 2004 study she conducted, a group of subjects consumed only vanilla-flavor Boost, a protein drink, for five days to assess their cravings for other food. She was amazed to find many of them craved Boost after returning to a regular diet: “We thought they’d never want to see it again.”
The same phenomenon occurs with movie-theater popcorn, Dr. Pelchat says: “Most people will admit it’s not the world’s best popcorn, but if the line is long and you’re not able to buy it, you may well crave it.”
Functional MRI scans by Dr. Pelchat showed that sensory memory food cravings activate the same parts of the brain that drug and alcohol cravings do, including the hippocampus, which helps store memories; the insula, involved in perception and emotion; and the caudate, which is important for learning and memory. The circuit is driven by dopamine, the neurotransmitter responsible for reward-driven learning.
Experts say that cravings are fine on occasion—say, for pumpkin pie at Thanksgiving, gingerbread at Christmas or for healthy choices year-round. But indulging too often can send cravings spiraling out of control.
Brain researchers have documented that when people continually bombard their reward circuits with drugs, alcohol or high-fat, high-sugar foods, many of the dopamine receptors in the system shut down to prevent overload. And with fewer dopamine receptors at work, the system craves more and more, insatiably. “Pretty soon, one cupcake doesn’t do it anymore. You have to overstuff yourself and you still don’t get that reward,” says Pam Peeke, a physician and author of the new book, “The Hunger Fix.” She notes that food addiction creates changes in the prefrontal cortex, which normally override impulsivity and addictive urges.
What is the best way to fight food cravings? Many studies have shown that the more subjects try to restrict a food, the more they may crave it. So some experts suggest embracing and controlling the urge instead.
One 2003 study at University College in London found that subjects who ate chocolate only in the middle of a meal or just after were more successful at giving it up than those who ate it on an empty stomach.
Cognitive behavior therapy can also be helpful. Researchers in Adelaide, Australia, gave 110 self-professed chocolate cravers each a bag of chocolates to carry around for a week, and instructed half of them in “cognitive restructuring”—challenging their thoughts about chocolate—while the other half learned “cognitive defusion”—accepting and observing their thoughts without acting on them. At the end, the defusion group had three times as much chocolate left than the other group.
Exercise can also cut food cravings. Women who walked briskly on a treadmill for 45 minutes had far less brain response to food images, according to a new study from Brigham Young University in Provo, Utah, published in the journal Medicine & Science in Sports & Exercise.
Other forms of distraction include chewing gum and smelling a nonfood item. Taking a deep whiff of jasmine, for example, helps occupy the same aroma receptors that are a key part of food cravings.
Dr. Peeke suggests setting a timer for 30 minutes whenever a craving comes on. Busy yourself with something else until the timer goes off. The craving may have passed. “If you can at least delay eating the craved food, you can weaken the habitual response,” agrees Dr. Pelchat.
The good news: The longer people stave off their food cravings, studies show, the weaker the urges become.
Write to Melinda Beck at HealthJournal@wsj.com