The efficacy of behavioral interventions to modify dietary fat and fruit and vegetable intake: a review of the evidence.
The evidence suggesting that nutrition, particularly dietary saturated fat and fruit and vegetable intake, is related to chronic disease risk has prompted considerable research on behavioral interventions focusing on dietary change. No clear understanding has emerged, however, of the degree to which these interventions can materially influence dietary change, or the types of intervention that are most effective and for whom. Therefore, the primary objective of the current study was to evaluate the overall effectiveness of behavioral dietary interventions in promoting dietary change related to chronic disease risk reduction. A secondary goal was to explore the relative effectiveness of specific intervention features and among different population subgroups. We conducted an evidence-based review and secondary analysis of existing literature. Our data sources included reports of randomized controlled trials and other study designs identified from multiple searches of MEDLINE, EMBASE, PsycINFO, CINAHL, AGELINE, and AGRICOLA. We included all studies on humans (including children, adolescents, and adults) published in English since 1975 that had been conducted in North America, Europe, or Australia; that had sample sizes of at least 40 subjects at follow-up; that were not based on controlled diets; and that otherwise met inclusion criteria. Through dual review, we abstracted detailed information on study characteristics, methodology, and outcomes relating to consumption of fruits, vegetables, and fats. From 907 unduplicated articles originally identified, we retained 104 articles reporting on 92 independent studies. The studies were similarly successful in reducing intake of total and saturated fat, and increasing fruit and vegetable intake. More than three-quarters of the studies (17 of the 22 reporting results for fruit and vegetable intake) reported significant increases in fruit and vegetable intake, with an average increase of 0.6 servings per day. Similar consistent decreases were seen in intake of saturated fat and total fat (7.3% reduction in the percentage of calories from fat). Interventions appeared to be more successful at positively changing dietary behavior among populations at risk of (or diagnosed with) disease than among general, healthy populations. Two intervention components seemed to be particularly promising in modifying dietary behavior-goal setting and small groups. The majority of the interventions reviewed resulted in meaningful improvements in dietary factors behaviors associated with the prevention of chronic disease, particularly among individuals at elevated disease risk. The lack of similarity across studies in outcome measures, study design, analysis strategy, and intervention technique hampered our ability to draw broad conclusions about the most effective behavioral dietary interventions, but our findings offer insight into intervention components that may hold promise for future research efforts.