Perceived behavioural control, unrealistic optimism and dietary change: an exploratory study.

In the context of five dietary changes conducive to reductions in fat consumption, a short questionnaire was constructed to examine the applicability of the theory of planned behaviour and to assess the presence of the phenomenon of "unrealistic optimism". An extension to the theory of planned behaviour was also included, in the form of a "self-identity" measure assessing identification with concern about the health consequences of diet. The questionnaire was completed by 612 members of the general public at three different locations in the U.K. The findings indicate some support for the applicability of the theory of planned behaviour, with the measure of "self-identity" producing some additional independent effects. Evidence of unrealistic optimism concerning diet-related health risks was found, with greater optimism being significantly related to lower relative consumption estimates of "unhealthy" foods. The findings are discussed in the context of implications for health promotion.