Elsevier

Preventive Medicine

Volume 46, Issue 3, March 2008, Pages 216-221
Preventive Medicine

Is physical activity a gateway behavior for diet? Findings from a physical activity trial

https://doi.org/10.1016/j.ypmed.2007.12.012Get rights and content

Abstract

Objective

While cross-sectional research indicates physical inactivity and poor diet tend to co-occur, there are limited longitudinal data on how interventions targeting one behavior affect other behaviors. The current investigation examined cross-sectional and longitudinal relationships between health behaviors within the context of a physical activity (PA) intervention.

Methods

Sedentary women (n = 280; mean age = 47.1; 94.6% Caucasian) were enrolled in a randomized controlled PA trial comparing the effects of print-based, individually-tailored and gender-targeted PA interventions to a wellness/control condition. Women completed baseline, month 3, and month 12 assessments that included measures of PA and dietary behaviors.

Results

Participants in more advanced PA stages of change reported significantly greater fruits/vegetables consumption than participants in less advanced stages, although the relationships between diet and minutes of weekly activity were less pronounced. The tailored and targeted print-based PA interventions had no effect on fruit/vegetable intake, although significant reductions in fat intake were observed from baseline (M = 31.24%) to month 3 (M = 30.41%), p < 0.03; and baseline to month 12 (M = 30.36%), p < 0.01. Changes in PA were not predictive of improvements in eating behaviors.

Conclusions

Although fat intake decreased in the context of this PA intervention, fruit/vegetable intake remained unchanged. Also, PA did not serve as a gateway behavior for dietary improvements. In fact, improvements in activity were associated with increases rather than decreases in fat intake.

Introduction

Physical inactivity and poor diet were responsible for 15.2% of deaths in 2000 (Mokdad et al., 2005), as these health risk behaviors are related to numerous cardiovascular disease outcomes, diabetes, obesity, and some cancers (American Cancer Society, 2003, Miller and Fletcher, 1998, Mokdad et al., 2003, Stunkard and Wadden, 1993, U.S. Department of Health and Human Services, 1996, Williams, 2001). Cross-sectional research has examined the relationships between these health behaviors and found significant associations between physical activity and consuming more fruits, vegetables, and fiber (Aranceta et al., 2001, Coulson et al., 1997, Eaton et al., 1995, Emmons et al., 2005, Matthews et al., 1997). Physical activity has also been inversely related to fat consumption (Eaton et al., 1995, Matthews et al., 1997, Simoes et al., 1995). However, such relationships have not always been demonstrated, leading some to conclude that these cross-sectional relationships are weak or non-existent (Blair et al., 1985a, Hartung et al., 1980, Voorrips et al., 1991).

Regarding the prospective relationships between health behaviors, some have proposed that physical activity may serve as a “gateway behavior” for other health behavior change, such as healthy eating (Blakely et al., 2004, Nigg et al., 1999, Tucker and Reicks, 2002). Thus, initial improvements in activity may lead the way for subsequent improvements in nutritional practices. There are a variety of reasons why physical activity could serve as a gateway behavior for dietary improvements. For instance, experiencing successful and positive behavior changes with physical activity could serve to promote individuals' self-efficacy and motivation to modify diet as well (Emmons et al., 1994). Similarly, as individuals realize the benefits associated with physical activity, they may be more motivated to increase these benefits by improving dietary behaviors (Tucker and Reicks, 2002). In the context of physical activity trials, participation in such a trial may raise participants' awareness of their health in general, resulting in more global changes beyond just the behavior targeted by the intervention (Wilcox et al., 2000). Alternatively, some individuals may be motivated to engage in physical activity as a means of weight loss. Since physical activity alone is only modestly effective in achieving weight reduction (Blair and Leermakers, 2002), individuals may adopt subsequent dietary changes as well to achieve desired weight outcomes.

Despite the rationale for such a relationship between diet and physical activity, there are minimal prospective data regarding the relationship between physical activity and eating behaviors. In one study examining naturally-occurring behavior changes, physical activity increases were associated with improved dietary behaviors, including fruit/vegetable, fat, and fiber consumption (Emmons et al., 1999). Similarly, a physical activity intervention resulted in significant decreases in calories, fat, and cholesterol (Wilcox et al., 2000). However, no changes were observed for fruit/vegetable or fiber intake, and the observed dietary changes were unrelated to improvements in activity (Wilcox et al., 2000). Blair et al. (1984) found that individuals voluntarily increasing their physical activity reported few differences in dietary changes compared with individuals who did not increase their activity. Although the gateway behavior hypothesis is based on the notion that behavior change occurs sequentially (i.e., changes in physical activity promote subsequent changes in diet), previous studies included cross-sectional examination of behaviors (Blakely et al., 2004, Tucker and Reicks, 2002), limiting the conclusions that can be drawn regarding this hypothesis.

In summary, the longitudinal findings regarding physical activity and dietary behaviors are mixed, and there is minimal research examining changes in eating behaviors following interventions that target physical activity. If interventions targeting physical activity also impact nutritional practices, this would have important implications regarding the impact and cost-effectiveness of such interventions. The purpose of this investigation was to examine the cross-sectional and longitudinal relationships between physical activity behavior, physical activity stage of motivational readiness for change, and specific eating behaviors (i.e., fruit/vegetable and dietary fat intake) among women enrolled in a randomized controlled physical activity trial. The effects of physical activity interventions on eating behaviors were examined, and the hypothesis that physical activity may serve as a gateway behavior for eating behaviors was tested.

Section snippets

Sample

The sample included 280 initially sedentary women between the ages of 18 and 65. Participants were recruited from two communities in Massachusetts via informational booths in supermarkets and health fairs, flyers distributed to local stores and libraries, local newspaper inserts, and public radio/cable service announcements. The institution's review board approved the study protocol.

Treatment conditions

Women were randomly assigned to receive one of three print-based interventions, including Jumpstart (an

Sample characteristics

Two hundred eighty women were enrolled in the randomized trial. Demographic characteristics of the sample are summarized in Table 1. There were no baseline differences in the demographic characteristics of the three treatment conditions. Physical activity and dietary values are summarized in Table 2. The current analyses include participants who completed the physical activity trial and had complete dietary data available at each follow-up, which represents 91% of the initial sample at month 3

Discussion

Most of the past research pertaining to relationships between physical activity and eating behaviors has included cross-sectional designs (e.g., Blakely et al., 2004, Tucker and Reicks, 2002), limiting conclusions that could be drawn about behavioral relationships across time. In addition to examining cross-sectional associations, the current investigation also explored the longitudinal relationships between physical activity and dietary behaviors in the context of a physical activity trial.

Conclusions

This investigation provides several novel findings related to the relationship between physical activity and dietary behaviors. This study is unique in its efforts to examine the effects of a physical activity intervention on eating behaviors and utilizing prospective data to test the gateway behavior hypothesis. While the physical activity interventions resulted in significant reductions in fat intake, diet generally changed independent of physical activity improvements. Thus, there was no

Acknowledgments

This project was supported by a grant from the Robert Wood Johnson Foundation (RWJF#044224). The American Heart Association provided the Choose to Move materials in-kind.

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