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Weight-Loss Outcomes: A Systematic Review and Meta-Analysis of Weight-Loss Clinical Trials with a Minimum 1-Year Follow-Up

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Abstract

Objective

To assist health professionals who counsel patients with overweight and obesity, a systematic review was undertaken to determine types of weight-loss interventions that contribute to successful outcomes and to define expected weight-loss outcomes from such interventions.

Design

A search was conducted for weight-loss–focused randomized clinical trials with ≥1-year follow-up. Eighty studies were identified and are included in the evidence table.

Outcomes measures

The primary outcomes were a measure of weight loss at 6, 12, 24, 36, and 48 months. Eight types of weight-loss interventions—diet alone, diet and exercise, exercise alone, meal replacements, very-low-energy diets, weight-loss medications (orlistat and sibutramine), and advice alone—were identified. By using simple pooling across studies, subjects mean amount of weight loss at each time point for each intervention was determined.

Statistical analyses performed

Efficacy outcomes were calculated by meta-analysis and provide support for the pooled data. Hedges’ gu was combined across studies to obtain an average effect size (and confidence level).

Results

A mean weight loss of 5 to 8.5 kg (5% to 9%) was observed during the first 6 months from interventions involving a reduced-energy diet and/or weight-loss medications with weight plateaus at approximately 6 months. In studies extending to 48 months, a mean 3 to 6 kg (3% to 6%) of weight loss was maintained with none of the groups experiencing weight regain to baseline. In contrast, advice-only and exercise-alone groups experienced minimal weight loss at any time point.

Conclusions

Weight-loss interventions utilizing a reduced-energy diet and exercise are associated with moderate weight loss at 6 months. Although there is some regain of weight, weight loss can be maintained. The addition of weight-loss medications somewhat enhances weight-loss maintenance.

Section snippets

Data Sources

For the purpose of conducting the systematic review, the central research question to be addressed was stated as: “Do weight-loss interventions (advice alone, diet alone, exercise alone, diet and exercise, meal replacements, very-low-energy diets, orlistat, and sibutramine) contribute to sustained weight loss/maintenance over time (ie, 6, 12, 24, 36, and 48 months)?” The PubMed (www.ncbi.nlm,nih.gov/entrez/query.fcgi) online database, along with the bibliographies of selected studies, was

Systematic Review

The initial literature review identified 1,797 citations for screening. Of these, 59 studies met inclusion criteria. During the screening process, another 21 articles were identified using the study bibliographies. Thus, a total of 80 studies were ultimately included in the review with 26,455 subjects enrolled and randomized. At the 1-year follow-up, the average participant attrition rate across studies was 29%. Overall, attrition was 31% at study end regardless of follow-up length.

Diet alone

Discussion

Based on the results of a systematic review of the literature, this study provides evidence that among completers of weight-loss clinical trials, interventions that include food and meal planning strategies—diet alone, diet and exercise, and meal replacements—resulted in a mean weight loss of approximately 5 to 8.5 kg (5% to 9%) from starting weight during the first 6 months. Weight-loss plateaus at approximately 6 months and stabilized to a weight loss of approximately 4.5 to 7.5 kg (4.8% to

Conclusions

Based on a systematic review of the literature, weight-management completers can expect to lose a modest amount of weight that will decrease their risk for developing chronic health problems. Weight-loss interventions involving attention to food intake—diet alone, diet and exercise, meal replacements, and weight-loss medications combined with diet—seem to produce the most encouraging short-term results. At approximately 6 months, weight loss begins to plateau across nearly all interventions,

M. J. Franz is a nutrition/health consultant with Nutrition Concepts by Franz, Inc, Minneapolis, MN.

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    M. J. Franz is a nutrition/health consultant with Nutrition Concepts by Franz, Inc, Minneapolis, MN.

    J. J. VanWormer is a program evaluation consultant at HealthPartners Health Behavior Group, Minneapolis, MN.

    A. L. Crain is a statistician at HealthPartners Research Foundation, Minneapolis, MN.

    J. L. Boucher is director of education, Minneapolis Heart Institute Foundation, Minneapolis; at the time of the study, she was director, Health Programs and Performance Measurement, HealthPartners Health Behavior Group, Minneapolis, MN.

    T. Histon is director of weight management initiative and W. Caplan is director of clinical development at Kaiser Permanente’s Care Management Institute, Oakland, CA.

    J. D. Bowman is manager of knowledge and information at A. Kaiser Permanente Innovation, Oakland, CA.

    N. P. Pronk is executive director, HealthPartners Health Behavior Group, Minneapolis, MN.

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