The aim of the present study was to describe the association of fast food consumption with BMI, energy intake and diet quality in a Mediterranean population. The subjects were Spanish men (n 1491) and women (n 1563) aged 25-74 years who were examined in 1999-2000, in a population-based cross-sectional survey in northeast Spain (Girona). Dietary intake was assessed using a FFQ that included four typical fast food items. Two dietary-quality indices, the Mediterranean diet score and the healthy eating index, were created. Height and weight were measured. Within the population studied, 10.1 % reported eating fast food at least once per month. Dietary energy intake and energy density were directly associated with frequency of fast food consumption. Multivariate logistic regression analysis adjusted for lifestyle and educational level showed an inverse association of frequency of fast food consumption with meeting the dietary reference intake (DRI) for energy (P = 0.001). The consumption of fast food more than once per week increased the risk of overall low diet quality (P < 0.001). BMI was directly associated with fast food consumption expressed in g/d (P = 0.025) and in kJ/d (P = 0.017). The risk of being obese increased with the frequency of fast food consumption (P = 0.046). Fast food consumption was associated with higher energy intakes, poor diet quality and higher BMI. The likelihood of not meeting the DRI for energy, and of being obese, increased with the frequency of fast food consumption.