Unhealthy diet is the leading preventable risk for poor health in New Zealand. Dietary risk factors such as low fruit and vegetable consumption, high salt intake, and obesity are also key drivers of health inequalities. However small improvements in diet across the whole population could produce major health gains, achieve cost savings, and reduce inequalities. This research will evaluate the effects of four priority action areas to improve diets: (1) a low-cost dietary salt reduction package for adults with high blood pressure; (2) co-designed, commercially sustainable supermarket intervention(s) to promote healthy food purchases; (3) the impact of voluntary front-of-pack nutrition labels (Health Star Ratings) on consumer food purchases and industry reformulation practices; and (4) a theory-driven advocacy campaign to improve the healthiness of processed foods. This research extends our previous work to improve population diets and has an explicit emphasis on practical interventions and translating findings into policy and action.