Background and Objectives: Low HDL concentrations are considered an important risk factor for cardiovascular disease. Interventions promoting a low-fat, plant-based eating pattern appear to reduce CVD risk while paradoxically also reducing HDL concentrations. Recent studies show HDL to comprise a range of subfractions, but the role these play in ameliorating the risk of CVD is unclear. The purpose of this study was to characterise changes in HDL subfractions in participants where HDL decreased following the CHIP intervention which promotes a low-fat, plant-based diet, with physical activity. Methods and Study Design: Individuals (n=22; mean age=55.4±16.3 years; 45.5% men, 54.5% women) participating in a CHIP intervention were assessed at baseline and 30 days for changes in BMI, blood pressure, lipid profile, (including large-, intermediate- and small-HDL subfractions) and fasting glucose. Results: HDL significantly decreased (10.6%, pConclusions: This paper discusses specific changes in HDL subfractions when overall-HDL decreases as a response to low fat, whole-food, plant-based eating and exercise. Additional research is required to elucidate the reasons through which behavioural therapies remodel the HDL particle and how this impacts the functional properties of HDL and CVD risk.