The effect of duration of intervention and locus of control on dietary change.

Scientific evidence supports a relationship between diet and the incidence of cancer. This finding has resulted in dietary recommendations that have been disseminated to the public. To reduce actual cancer incidence, these recommendations must lead to dietary changes among the population. We compared two brief dietary interventions with a longer term intervention and found that all three interventions produced significant reductions of calories, fat, fiber intake, and weight. The duration of the intervention did not significantly affect the magnitude of these reductions. We also found that health locus of control did not affect dietary change. Participants who initially were found to have an internal locus of control, or who subsequently internalized their locus of control during the period of observation, did not demonstrate a significant change in their intake of any of the nutrients measured when compared to participants with an external locus of control. Thus, we suggest a brief dietary intervention as a feasible and effective mechanism to produce progressive incremental dietary changes in a large population.