Cardiometabolic diseases are highly prevalent in Aotearoa New Zealand(1). Dietary intake is a modifiable risk factor for such diseases and certain dietary patterns, specifically the Mediterranean diet (MedDiet), are associated with improved metabolic health(2). This study aims to test whether an intervention of a Mediterranean dietary pattern incorporating high quality New Zealand foods (NZMedDiet pattern) using behaviour change science can improve the metabolic health of participants and their household/whānau. This is a multi-centre, three-stage trial, with two randomised controlled trials (RCTs), both parallel groups, superiority trials, and a longitudinal cohort study. The first RCT (RCT1) is a comparison of the NZMedDiet pattern implemented using behaviour science compared to usual diet for 12 weeks, and the second (RCT2) is a behaviour-change intervention compared to no intervention for 12 weeks, administered after participants have been exposed to the intervention in RCT1. The third stage is a longitudinal cohort study where all participants are followed for up to a year. The primary outcome measure for each stage is the metabolic syndrome severity score (MetSSS). Two hundred index participants and their household/whānau have been recruited and randomised into the trial. Participants are from four centres, two of which are University research units (University of Auckland (n = 57) and University of Otago, Christchurch (n = 60)), one a community-based traditional meeting place (Tu¯ Kotahi Māori Asthma and Research Trust at Ko¯kiri Marae in Lower Hutt, Wellington (n = 19)), and the other based at a hospital-based research unit (the Centre for Endocrine Diabetes and Obesity Research (CEDOR) in Wellington (n = 64). The trial will test whether the NZMedDiet pattern and behaviour change support improves the cardiometabolic health of people in New Zealand.