LINE ON LIFE

9/6/92

Causes of Cravings *

David A. Gershaw, Ph.D.

Although our physiology effects our eating, research reveals that social factors play a great role in our food cravings and aversions. What are these factors?

In the first years of life, biology typically rules. If offered a wide variety of foods, infants typically regulate their nutritional needs by varying what they eat. In an experiment of psychologist Leann Birch, the formulas of six-week-old babies were diluted excessively with water. In response, the babies drank much more formula, so they could get the needed nutrients.

In contrast, social forces can affect eating habits as early as the age of 2. Birch's more recent studies indicate that tactics used by parents to get their children to eat "properly" may backfire. Some parents inadvertently cause some weird cravings. The usual tactic of rewarding with dessert if they finish a certain food "If you eat your vegetables, you may have some dessert." works only in the short term. According to Birch, since this coercion suggests that there might be something wrong with the food they had to finish, they may dislike this food in the long run. In contrast, the food used for the reward tends to be liked even more. Unfortunately, it is typically a fattening dessert.

In addition, some parents distort how much food the child needs by using adult portions to judge how much a child "should" eat. According to Birch

"A 2-year-old only needs two teaspoons of peas, not a half cup. It can be destructive to make a child finish everything in his plate, especially if the portions are too big. Coercion backfires. If you focus on external factors, like how much food is left on the plate, or what time it is, then children get out of touch with their internal cues for when they are hungry and when they are full."

Obese adults who continually go off and on diets are unaware of bodily cues for hunger or fullness. They tend to have parents who insisted on eating only at certain times or who coerced them to finish their food. (I remember being told to clean my plate to help the starving people in Europe.) As Birch says

"If your parents say it's not time to eat yet when you tell them you're hungry, or insist you finish what's on you're plate when you're already full, it can lead you to look for external cues to decide when and how much to eat, and that creates life-long weight problems. Natural eaters, in contrast, eat when they're hungry and stop when they're full. They rarely have weight problems."

Another problem is getting children to eat something new. Generally children prefer familiar foods and hesitate to try new ones. Rather than accepting the child's initial "I don't like it," get the child to taste the food. It may take 10 tastes at 10 different times to make the food familiar and acceptable to the child, but it can be done.

With 2-to-5 year-olds, another method works even better. Have them eat with several other children who like the food. They soon will begin to prefer it, even weeks later, when the other children are not there.

Some people believe that they can sense needed nutrients in foods, so they naturally develop a craving for that food. Although our senses can detect salt and sugar in our foods, we cannot taste or smell the proteins, carbohydrates, fats or vitamins. This limits special cravings to salt and sugar.

When experiments in the 1950s deprived rats of various nutrients, they did not automatically seek out a food that had the nutrient. In contrast, they had a tendency to choose foods that were novel. By trial-and-error, they finally found something that provided the missing nutrient. When found, this food became preferred until their need was met. A similar response probably exists in humans whether they are young children, adults or pregnant women.

The opposite of craving is aversion. When you get sick after eating a meal, you develop an aversion to whatever food had the most distinctive flavor whether or not it caused your illness. A similar process might cause children to dislike various foods. By chance, these illnesses might occur after the children have eaten foods with distinctive flavors. Under these conditions, it is easy to understand how aversions can develop.

Of course, biology still affects our cravings. Mechanisms that served our ancestors might sabotage us. Previously, essential nutrients like fats, sugars and salts were scarce in nature. To survive, we needed these foods. Now even with the plentiful supply of these nutrients in our modern life we still have built-in cravings for fats and sugars.

In a recent experiment, people who were hungry not starving tended to become pickier in what they ate. Unfortunately, they preferred the better-tasting foods high in fats and sugars. As one researcher put it, "It is unfortunate for dieters. The body is not designed to lose weight."


* Adapted from Daniel Coleman's "What's for Dinner? Psychologists Explore Quirks and Cravings," The New York Times, July 11, 1989.

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