Evidence suggests that the workplace is a potentially effective setting for interventions to reach a large number of people from different professions and socio-demographic backgrounds and promote dietary behaviour change. As businesses are likely to benefit from healthier staff, employers are recognising the potential that supporting staff in leading healthier lifestyles may have and are becoming increasingly supportive of workplace wellbeing programmes. However, most evidence on behaviour change in the workplace comes from interventions addressing multiple health behaviours, making it difficult to draw conclusions on effective diet-related strategies. The main focus of this thesis has been to evaluate the effectiveness of nutrition workplace interventions on diet-, health- and work-related outcome measures; to identify demographic characteristics that may influence food choice in working populations; and the barriers and motivators of catering establishments to provide healthier food options.