The impact of job strain on the predictive validity of the theory of planned behaviour: an investigation of exercise and healthy eating

Objectives. This study examined the impact of the job strain model on exercise and healthy eating within the framework of the Theory of Planned Behaviour.
Design. Participants completed a questionnaire measuring the components of the Theory of Planned Behaviour and the job strain model. A follow-up questionnaire a week later measured behaviour.
Method. The questionnaires were completed by e-mail. The initial questionnaire was completed by 331 employees, and 286 follow-up questionnaires were returned.
Results. Job demands affected exercise indirectly by lowering perceptions of behavioural control over exercise. However, variables from the job strain model were not related to exercise intentions or behaviour. In contrast, employees in passive jobs intended to eat more sweets and snack foods and employees in low strain jobs were more likely to realize their intentions to eat more sweets and snack foods. However, variables from the job strain model did not influence consumption of fruit and vegetables.
Conclusions. While people may consider the impact of job strain on exercise whilst making decisions about whether or not to exercise, job strain has a more direct impact on healthy eating. However, job strain may only affect consumption of so-called `high density' foods, rather than foods such as fruit and vegetables.