Herman and Mack's restrain theory explains why dieting can lead to over-eating. According to the boundary model, hunger keeps our intake of food above a certain minimal level, and satiety keeps our intake below the maximum level.
Dieters tend to have a larger range berween hunger and satiety leveks as it takes them longer to feel hungry and more food to satisfy them.
Restrained eaters also have a self-imposed desired intake. Once they have gone over this boundary they continue to eat until they reach satiety.
The role of denial
Cognitive psychology has shown that trying to suppress or deny a thought often makes it more prominent.
Wegner asked some participants not to think about a white bear, but to ring a bell if they did, and others to think about the bear. Those told not to think about the bear rang their bells far more often. Wegner calls this the 'theory of ironic processes of mental control' - in other words denial often backfires.
Dieting always involves the decision not to eat certain foods, or to eat less of them. As dieters try to suppress their thoughts about these 'forbidden' foods, their preoccupation with these foods increases, makeing those foods more attractive and desirable.
The success of dieting
Redden suggests that, in order to be successful at dieting, people need to pay attention to the details of what they are eating. People usually enjoy experiences less the more they repeat them, and when it comes to dieting this can make it harder to stick to particular foods. He suggests that, instead of thinking something like 'oh no not another salad' we focus on the details of the meal. Doing this reduces boredom and makes it easier to stick to a diet.
Redden tested this theory with the jelly beans experiment. He gave 135 people 22 jelly beans each, one at a time. As each bean was dispensed, information about it was flashed onto a computer screen. One group saw general information whereas the others were given specific flavour information. Participants given specific info enjoyed the task more.