Comparison of 2-Year Weight Loss Trends in Behavioral Treatments of Obesity: Diet, Exercise, and Combination Interventions

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Abstract

Objective The effects of three cognitive-behavioral weight control interventions for adults were compared: diet only, exercise only, and a combination of diet and exercise. This article reports 2-year follow-up data.

Design The three interventions were compared in a randomized, experimental design.

Subjects A total of 127 men and women who were at least 14 kg overweight (according to height-weight tables) were recruited from an urban community and assigned randomly to the experimental conditions.

Intervention The dietary intervention was a low-energy eating plan adjusted to produce a 1 kg/week loss of weight. The exercise component involved training in walking and a home-based program of up to five exercise periods per week. There were 12 weekly instructional sessions, followed by 3 biweekly and 8 monthly meetings. All sessions were led by registered dietitians.

Outcome measures Changes in body weight.

Statistical analyses Analysis of variance for weight changes and repeated measures analysis of variance for weight change trends.

Results At 1 year, no significant differences were noted among the three groups. The diet-only group lost 6.8 kg, the exercise-only group lost 2.9 kg, and the combination group lost 8.9 kg (P=.09). During the second year, the diet-only group regained weight — reaching 0.9 kg above baseline; the combination group regained to 2.2 kg below baseline; and the exercise-only group regained slightly to 2.7 kg below baseline (P=.36). Repeated measures analysis of variance showed a group-by-time interaction (P=.001); data for the dieting groups best fit a U-shaped regain curve (P=.001).

Applications The results suggest that dieting is associated with weight loss followed by regain after treatment ends, whereas exercise alone produced smaller weight losses but better maintenance. The large outcome variability and unequal difficulty of the regimens across groups limit the generalizability of the findings. J Am Diet Assoc. 1996; 96:342-346.

Section snippets

Procedures and Subjects

The study sample consisted of men and women between the ages of 25 and 45 years who volunteered for an obesity treatment program. Subjects were recruited from the metropolitan area of Houston, Tex, through media announcements. The study protocol was approved by the institutional review boards of Baylor College of Medicine and the Methodist Hospital. Subjects were at least 14 kg overweight and not currently engaged in regular exercise. Each subject deposited $100 in an account, which was

Statistical Methods

Preliminary analysis using the ÷2 statistic (19) compared the three treatment groups by sex and by availability for follow-up.

To evaluate the potential for selection bias, an analysis of variance (ANOVA) model was applied that included treatment group and loss to follow-up as main effects and interaction terms. Participants who were available for follow-up and those who were lost to follow-up were compared in terms of these dependent variables: initial body weight, ideal body weight, initial

Attrition

Attrition over the course of the study is shown in (Table 1). Of the 127 subjects who were randomly assigned to the three treatment conditions, 86 remained with the treatment program throughout its 1-year duration. Preliminary evaluation indicated that, at the end of 1 year, the three treatment groups did not differ by sex (÷2=0.16; df=2- P=.924); ideal body weight, which was defined as mean weight for height and medium frame from the Metropolitan tables (20) (ANOVA F=0.02; df=2.82; P

Discussion

This study addressed the hypothesis that the combination of diet and exercise is the most effective behavior modification treatment for long-term weight control. The study was designed to compare the effects of treatment condition (diet only, exercise only, and the combination of diet and exercise) on the success of weight loss and maintenance by overweight, free-living adults 2 years after enrollment in a behavior modification program. No significant difference in weight status was noted among

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