Research that Changed Research: Restrained and Unrestrained Eating

We know that everyone has different eating habits. Some people eat very little to feel full while others eat a lot. And considering the spectrum of disordered eating, we know that some people eat less than or more than they should. However, is there something different about the eating behavior of people of different sizes, such as that of an overweight individuals? Herman and Mack’s classic experiment with milkshakes and ice cream provided a breakthrough response in their study “Restrained and Unrestrained Eating.”

In this study, 45 subjects were randomly assigned to three preload conditions: 0 milkshakes, 1 milkshakes, or 3 milkshakes. After the preload, subjects were give three 3-pint container of ice cream in chocolate, vanilla, and strawberry flavors. The subjects were simply told that the experiment was a “taste” test, and were given the instruction to rate each flavor. After the ratings were provided, subjects were welcomed to eat as much ice cream as they want until the ten minute time mark. A eating habit questionnaire was administered after the taste ratings.

Of course, the actually variable being measured is the amount of ice cream eaten after the preload. The data showed that those with high restraint consumed more ice cream after a preload while those with low restraint consumed decreasing amount of ice cream depending on the amount of preload. The following passage is from the original article:

“In any event, we may conclude that despite the weak correlation between restraint and percent overweight, it is the dimension of restraint that is the best predictor of behavior in the present (and presumably, analogous) circumstances. By extension, it seems reasonable to conclude, at least tentatively, that restraint rather than simply a large degree of overweight is the critical variable governing the eating behavior of obese individuals. Our small sample of obese subjects was not homogeneous with respect to restraint, and behavior varied accordingly. Presumably, those studies detecting obese/normal differences have “capitalized” on corresponding differences in restraint.”

Herman and Mack’s experiment demonstrated that restrained eaters eat excessively more only when they violated their diet. More importantly, this paradigm set the stage for future eating research, even Dr. T’s  study  “Consumption After a Diet Violation Disinhibition or Compensation?” where she tested whether or not restrained eaters are able to control their eating behavior outside of an artificial setting. Dr. T found that even after a diet violation, restrained eaters do not overeat in everyday life (Read more).