Review and special article
Telephone Interventions for Physical Activity and Dietary Behavior Change: A Systematic Review

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Background

Given the epidemic of lifestyle-related chronic diseases, building the evidence base for physical activity and dietary behavior change interventions with a wide population reach is of critical importance. For this purpose, telephone counseling interventions have considerable potential.

Purpose

To systematically review the literature on interventions for physical activity and dietary behavior change in which a telephone was the primary method of intervention delivery, with a focus on both internal and external validity.

Methods

A structured search of PubMed, Medline, and PsycInfo was conducted for studies published in English from 1965 to January 2006. Studies targeted primary or secondary prevention in adults, used randomized designs, and included physical activity and/or dietary behavior outcomes.

Results

Twenty-six studies were reviewed, including 16 on physical activity, six on dietary behavior, and four on physical activity plus dietary behavior. Twenty of 26 studies reported significant behavioral improvements. Positive outcomes were reported for 69% of physical activity studies, 83% of dietary behavior studies, and 75% of studies addressing both outcomes. Factors associated with positive outcomes appear to be the length of intervention and the number of calls, with interventions lasting 6 to 12 months and those including 12 or more calls producing the most favorable outcomes. Data on the representativeness of participants, implementation of calls, and costs were reported much less frequently.

Conclusions

There is now a solid evidence base supporting the efficacy of physical activity and dietary behavior change interventions in which the telephone is the primary intervention method. Thus, research studies on broader dissemination are necessary, and should address questions relevant to the translation of this body of work into population health practice.

Introduction

Physical activity and dietary behavior changes are important to the primary prevention and management of all prevalent chronic conditions. Together they account for 17% of overall disease burden in the United States.1 The population prevalence of insufficient physical activity and inadequate diet is high among adults in industrialized countries.2, 3, 4 This, combined with epidemic rates of lifestyle-related diseases and high rates of overweight and obesity, underline the imperative to develop population-based approaches to address these key health behaviors.

There is now a large evidence base supporting the efficacy of physical activity and dietary behavior interventions for adults, across a range of settings and target populations, and utilizing a range of intervention modalities.5, 6, 7, 8 Many of these delivery modalities, including mailed print materials, computer-tailored interventions, and Internet-delivered interventions, have the potential for wide population reach. Telephone-delivered interventions for physical activity and dietary behavior change also have this potential. The telephone remains one of the most widely available communication tools, and is likely to remain so for the foreseeable future. Telephone-delivered health behavior interventions also have the potential for being adopted by the growing number of government and nongovernmental agencies and health maintenance organizations that operate telephone information, support, and triage centers.9 It is thus important that we understand what can be achieved via this important health behavior intervention delivery mechanism.

Over the past decade, telephone-delivered interventions have been evaluated across several health behaviors, especially cigarette smoking. McBride and Rimer10 provided a descriptive review of this broader literature in 1999, focusing on telephone-delivered interventions across a number of health behaviors (i.e., smoking, cancer screening, lifestyle behaviors), including 74 studies. They concluded that there was the most evidence for smoking cessation and cancer screening, but that the potential for population reach was limited; higher educated, white women were over-represented across the studies reviewed. Only six of the studies described were on physical activity or dietary behavior change, and thus they did not offer conclusions specific to telephone interventions in these areas. In 2001, Castro and King9 synthesized the findings of seven studies from the Stanford research program that used the telephone to increase physical activity, and concluded that there was strong evidence in support of such interventions.

Since the publication of these reviews, the number of studies of telephone-delivered interventions for physical activity and dietary behavior change has continued to grow. However, there has been no systematic review of this literature. The extant studies now make it possible to conduct such a review. It is also now possible to evaluate empirically a number of issues that were proposed by McBride and Rimer10 and Castro and King9 as directions for future research, including the optimal type and intensity of interventions, as well as the extent to which they can be used to reach underserved populations.

It is important to note that pure telephone-delivered interventions are rare, with most being supplemented with other intervention components, such as an initial face-to-face session or print materials. Thus, the purpose of this review is to inform the next generation of research on physical activity and dietary behavior change interventions in which the telephone is the primary method of intervention delivery. We begin by evaluating the strength and quality of the evidence base, with a focus on internal validity consistent with guidelines for systematic reviews.11 However, we also give strong emphasis to an evaluation of the extent to which this body of literature informs translation into practice (external validity), something less common in systematic reviews. This second aspect is guided by elements of the RE-AIM Framework (reach, efficacy, adoption, implementation, maintenance), which provides an approach to evaluation that balances internal and external validity.12, 13

Seven specific questions are addressed in this systematic review: (1) What is the evidence for including telephone counseling in interventions for physical activity and dietary behavior, as well as for combined interventions? (2) Does the use of other intervention components (e.g., face-to-face sessions, print materials) improve the efficacy of telephone-delivered interventions? (3) What is the optimal number of calls and duration of intervention? (4) Are telephone counseling interventions robust across different interventionists? (5) What is the participation rate (reach) of telephone counseling interventions, and are they reaching representative (and underserved) populations? (6) To what extent are interventions being implemented according to stated protocols? and (7) Are intervention delivery cost data (or cost-effectiveness analyses) being reported?

From answers to these questions, a number of research questions for future studies are derived; these focus on how best to inform the translation of findings into public health practice.

Section snippets

Methods

The study protocol was based on guidelines from the Cochrane Reviewers’ Handbook11 and adapted from a recently published review of computer-tailored physical activity and dietary behavior change interventions.14 Eligibility criteria were made explicit (described below) and the first author (EE) and the second author (SL) independently reviewed the articles and abstracted data. Disagreements were discussed with the other coauthors until consensus was reached.

Study Selection

The search across the three databases yielded 879 publications. After eliminating duplicates and reviewing all abstracts, the total number was reduced to 89 publications. Checking the references in these publications produced another five studies. After completely reviewing the 94 articles, 69 were excluded, as they did not meet all of the inclusion criteria. A large proportion of the articles excluded had no dietary behavior or physical activity outcomes, the telephone was not the primary

Discussion

Our systematic review found the evidence for physical activity and dietary behavior interventions that predominantly use telephone counseling to be quite strong, with 20 of 26 studies reporting significant positive changes in the target behavior. The average effect size across studies (0.60) was moderate.15 When evaluated by specific behavioral targets, support for telephone counseling interventions is strong for those targeting dietary behavior, and good for those targeting physical activity,

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