This paper quantifies the impact of consumer’s diet-health behaviours on an important health outcome. We use data from the 2007-2008 U.S. NHANES to estimate the impact of dietary supplement intake on respondent’s BMI outcomes, controlling for diet quality using Healthy Eating Index scores. The analysis applies propensity score matching (PSM) to account for selection bias and endogeneity between self-reported diet and health behaviour (treatment) and BMI outcomes. Dietary supplement choices are explained by demographic, lifestyle, food culture and food security variables. Matching results suggest that regular dietary supplement consumption is associated with significant lower BMI outcomes of almost 1 kg/m2.