The Psychology of Eating: From Healthy to Disordered Behavior

Dieting 131

The causal analysis of overeating

The causal analysis of eating behavior was first described by Herman and
Polivy (Herman and Mack, 1975; Herman and Polivy, 1980, 1988; Polivy
and Herman, 1985). They suggested that dieting and bingeing were causally
linked, and that “restraint not only precedes overeating but contributes to
it causally” (Herman and Polivy, 1988, p. 33). This suggests that attempt-
ing not to eat, paradoxically, increases the probability of overeating, the
specific behavior dieters are attempting to avoid. The causal analysis of
restraint represented a new approach to eating behavior, and the prediction
that restraint actually caused overeating was an interesting reappraisal of
the situation. Wardle further developed this analysis (Wardle, 1980), and
Wardle and Beales (1988) experimentally tested the causal analysis of overeat-
ing. They randomly assigned 27 obese women to either a diet group, an
exercise group, or a no-treatment control group for 7 weeks. At weeks 4
and 6, all subjects took part in a laboratory session designed to assess their
food intake. The results showed that subjects in the diet condition ate more
than both the exercise and the control group, supporting a causal link between
dieting and overeating. From this analysis, the overeating shown by dieters
is actually caused by attempts at dieting.

The boundary model of overeating

In attempt to explain how dieting causes overeating, Herman and Polivy
(1984) developed the “boundary model,” which represented an integration
of physiological and cognitive perspectives on food intake. The boundary
model is illustrated in figure 7.4.
The boundary model suggests that the food intake of restrained eaters
is regulated by a cognitively determined “diet boundary.” It indicates that
dieters attempt to replace physiological control with cognitive control
which represents “the dieter’s selected imposed quota for consumption on
a given occasion” (Herman and Polivy, 1984, p. 149). Herman and Polivy
(1984) described how after a low-calorie preload the dieter can maintain
her diet goal for the immediate future since food intake remains within
the limits set by the diet boundary. However, after the dieter has crossed
the diet boundary (i.e., eaten something “not allowed”), they will consume
food ad libitumuntil the pressures of the satiety boundary are activated.
The boundary model proposes a form of dual regulation, with food intake