Your final term paper is due the next morning, but you can't type another word unless you get a slice of hot, gooey tomato and spinach pizza. You run over to the student union, even though it will put you behind schedule.
You've gotten to the movie theater late and just found a place to sit when suddenly you have to have hot, buttered popcorn, even though you know that if you get it, you'll miss the first 10 minutes of the feature.
It's time for your menstrual cycle to begin and nothing will satisfy your midnight hunger, except chocolate ice cream. So you head out to the local convenience store on a snowy night.
Marcia Pelchat, a biological psychologist at Philadelphia's Monell Chemical Senses Center who looks at how people make food choices, says part of what characterizes food cravings is a desire so strong that you'll go out of your way to satisfy it. But beyond that researchers are hard-pressed to define cravings with any rigid scientific criteria. And that makes it hard to understand how, and to what degree, they influence what we eat.
Cravings Not Tied to Nutrients
One thing seems pretty certain: They're not based on specific nutrient needs, as many people suspect. That is, if you crave potato chips, it's not because your body needs the salt they contain. And if a man craves a high-protein food like steak or a burger, it's not because his body is telling him to stockpile protein for his muscles.
Craving a food for your health is "a much nicer story" than craving a food simply because you feel like eating it, says Richard Mattes, a professor of foods and nutrition at Purdue University who, like Pelchat, studies the hows and whys of people's food choices. "But the literature just does not suggest that."
Take salt cravings, for example. Mattes points out that even in studies where people were "depleted of sodium through heroic means" such as being put on diuretics, "they didn't really express a craving for sodium," a component of salt. Further, he notes, at the beginning of the century, miners who lost excessive amounts of sodium by sweating profusely during hard labor "had to be threatened with physical violence by their supervisors to get them to take their salt capsules." Even in cases of Addison disease, a very rare condition in which sodium levels become dangerously low, only 15% of patients crave salt, Mattes says.
On the flip side of the same coin, Monell's Pelchat points out that Americans in general consume thousands of milligrams of sodium a day, when the body requires only about 500. In other words, the desire for more sodium far outweighs any need for the mineral.
Are Hormones to Blame?
But what about women and their desire for chocolate at certain points during the menstrual cycle? That theory is floating around (remember Debra Waterhouse's book).
The problem: Plenty of foods contain carbohydrates. So why aren't women craving bran flakes?
It's not that women don't have cravings around the time of their menstrual flow; that association has been very well documented. It's just that what they crave doesn't appear to have anything to do with physiologic need. It's the same for cravings during pregnancy. Many women certainly experience them. But no one has been able to connect the dots between the foods craved and the mother's or baby's health.
Familiarity May Cause Cravings
As for why so many cravings are for chocolate, Mattes notes that's largely a Western phenomenon. "The study burning in my back pocket that I haven't done," he says, would be to look at chocolate cravings throughout the world. "I would be willing to bet that if you do a study on cravings in Asian countries, you'd find nothing special about chocolate," he states. "It's a Western-culture food."
"Through repeated exposure, a food becomes preferred," Mattes points out. "Familiarity begets acceptability," and acceptability begets cravings. "You crave things that you've had positive experiences with," he explains.
"The Japanese," he says, "show a preference for MSG [monosodium glutamate, a flavor enhancer] in relation to the U.S. population." But little is written about cravings for MSG because most of the research on cravings has been done in the United States and Canada. And in those two countries, at least, chocolate is the number-one craved food. Pizza is number two. In other words, as Mattes puts it, calorie-rich foods are "the most common" food-craving targets.
Cravings Shouldn't Cause Weight Gain
But, he points out, cravings are not thought to cause people to become overweight. When talking about cravings, he says, "you're usually referring to the overconsumption of a specific food. Overweight," on the other hand, tends to come from "small but sustained increases in food intake in the general diet."
Cravings aren't even believed to wreck weight-loss diets, at least not diets that people are able to follow over the long term. Research suggests that while people may be tempted by cravings when they first embark on a weight-loss plan, the cravings tend to wane over time. Even the initial cravings can be "tamed" to some degree, by making sure the diet's not too restrictive and too monotonous. The fewer foods a person is "allowed" on a weight-loss regimen, the more frequent—and intense—the cravings will tend to be.
If you're not trying to lose weight (or are not on a medically restricted diet that makes certain foods off limits), let the craving win, the experts advise. That will help keep it from getting out of hand. Indeed, says Mattes, "you'll probably do more psychological damage by denying a craving than nutritional damage by indulging it."