176 Obesity
episodes of under- and overeating resulting from dieting are translated into
fluctuations in weight. There is also some evidence that overeating is also
reflected in weight gain, particularly in women. For example, French et al.
(1994) reported the results from a cross-sectional and longitudinal study
of 1,639 men and 1,913 women who were involved in a worksite intervention
study for smoking cessation and weight control. The cross-sectional analysis
showed that a history of dieting, current dieting, and previous involvement
in a formal weight loss program were related to a higher body weight in
both men and women. Similarly, the prospective analysis showed that
baseline measures of involvement in a formal weight loss program and diet-
ing predicted increases in body weight at follow-up. However, this was
for women only. In particular, women who were dieting or who had been
involved in a formal weight loss program at baseline gained nearly 2 lbs
more than those who had not. Klesges, Isbell, and Klesges (1992) reported
similar results in their study of 141 men and 146 women who were followed
up after one year. The results showed that both the dieting men and women
were heavier than their nondieting counterparts at baseline. Higher base-
line weight and higher restraint scores at baseline also predicted greater
weight gain at follow-up in women. Dietary restraint is therefore associated
with weight fluctuations in dieters of both genders and overall weight gain
in women. If dieters perceive themselves to be overweight, but are not
necessarily obese, and if dieting causes overeating and subsequent weight
gain, then dieting could predictably play a causal role in the development
of obesity. It is possible that dieting also results in the relative overcon-
sumption of high-fat foods as these are the foods that dieters try to avoid.
What does all this research mean?The evidence for the causes of obesity is complex and can be summarized
as follows:
- There is good evidence for a genetic basis to obesity. The evidence for
how this is expressed is weak. - The prevalence of obesity has increased at a similar rate to decreases in
physical activity. - Low levels of activity predict weight gain at follow-up.
- There is some evidence that the obese exercise less than the nonobese.
- The prevalence of obesity has increased at a rate unrelated to the
overall decrease in calorie consumption.