128 Obesity
1.4 kg among the overall population. Furthermore, the preva-
lence of obesity was lowest among men who maintained a
relatively high level of vigorous physical activity, compared
to those who were relatively sedentary. These data show that
increased physical activity may prevent weight gain.
By fostering decreased energy expenditure and increased
energy consumption, modern environments have promoted
increases in body weights and in the prevalence of obesity.
Eaton and Konner (1985) have noted that there is a signi“-
cant mismatch between modern lifestyle and the lifestyles for
which humans (and our genes) evolved over tens of thou-
sands of years. This discordance has produced •diseases of
civilizationŽ as typi“ed by the current epidemic of obesity.
Prior to the past century, periodic shortages of food plagued
most societies, and obesity was rarely a problem. From an
evolutionary perspective, the scarcity of food acted as an
agent of natural selection. Because body fat serves primarily
as a reserve source of energy, genetic traits that contribute to
the accumulation of fat stores served an adaptive role by en-
hancing the chances of survival in times of scarcity. In mod-
ern societies, there are no intervals of scarcity to periodically
reduce the buildup of body fat. As a result, the constant and
abundant supply of food, coupled with lower levels of physi-
cal activity and energy expenditure, has led to dramatic in-
creases in the prevalence of overweight and obesity.
TREATMENT OF OBESITY
National surveys indicate that substantial numbers of
Americans are trying to lose weight. Recent data show that
about 44% of women and 29% of men report that they are
currently dieting to lose weight (Serdula et al., 1999). Most
people try to lose weight on their own (Jeffery, Adlis, &
Forster, 1991). Those who seek professional treatment exhibit
higher levels of distress and are more likely to be binge eaters
than obese persons in the general population (Fitzgibbon
et al., 1993). The options commonly available for profes-
sional treatment of obesity include lifestyle interventions
(typically a combination of behavior therapy, low-calorie
diet, and exercise) and more aggressive interventions includ-
ing pharmacotherapy and surgery.
Lifestyle Interventions
Behavior modi“cation procedures have become the founda-
tion of lifestyle interventions for weight loss (Wadden &
Foster, 1992). Participants in behavioral treatment are taught
to modify their eating and exercise habits so as to produce
weight loss through a negative energy balance. The key
components typically used in behavioral interventions in-
clude: (a) goal setting and daily self-monitoring of eating and
physical activity; (b) nutritional training aimed at the con-
sumption of a balanced low-calorie diet suf“cient to produce
a weight loss of 0.5 kg per week; (c) increased physical
activity through the development of a walking program
and/or increased lifestyle activities; (d) arrangement of envi-
ronmental cues and behavioral reinforcers to support changes
in eating and exercise behaviors; (e) cognitive restructuring
techniques to identify and change negative thoughts and feel-
ings that interfere with weight-loss progress; and (f ) training
in problem solving or relapse prevention procedures to en-
hance coping with setbacks and obstacles to progress.
More than 150 studies have examined the effects of be-
havioral treatment of obesity. Reviews of randomized trials
conducted since 1985 (Jeffery et al., 2000; NHLBI, 1998;
Perri & Fuller, 1995; Wadden, Sarwer, & Berkowitz, 1999)
show consistent “ndings. Behavioral treatments (typically
delivered in 15 to 26 weekly group sessions) produce mean
weight losses of approximately 8.5 kg and 9% reductions in
body weight. Attrition rates are relatively low, averaging
about 20% over six months. Negative side effects are uncom-
mon, and participants typically report decreases in depressive
symptoms. In addition, bene“cial changes in blood pressure,
glucose tolerance, and lipid pro“les typically accompany
weight reductions of the magnitude produced by behavioral
treatment (NHLBI, 1998; Pi-Sunyer, 1999). Thus, lifestyle
interventions are recommended as the “rst-line of profes-
sional intervention in a stepped-care approach to the manage-
ment of overweight and obesity (NHLBI, 1998).
The long-term effectiveness of lifestyle interventions has
remained an area of considerable concern. During the year
following behavioral treatment, participants typically regain
30% to 40% of their lost weight (Jeffery et al., 2000; Wadden
& Foster, 2000). Perri and Corsica (2002) summarized the re-
sults of behavioral treatment studies with follow-ups of two
or more years and found a reliable pattern of gradual weight
regain during the years following behavioral treatment.
Nonetheless, the data show a mean weight loss of 1.8 kg from
baseline to follow-ups conducted on average 4.3 years after
treatment.
Several considerations must be taken into account in eval-
uating the long-term results of weight-loss interventions.
Findings of small net losses or a return to baseline weights at
long-term follow-up need to be viewed in the context of what
might have happened had the obese individual never entered
treatment. Secular trends clearly show that the natural course
of obesity in untreated adults entails steady weight gain
(Shah, Hannan, & Jeffery, 1991). Hence, long-term “ndings
that show the maintenance of small amounts of weight loss