INTRODUCTION: vegetarian diets have been associated with lower risk of cardiovascular disease and a more favourable lipid profile in vegetarians who follow these diets for a long term period in observational studies, but the short-term effects of vegetarian diets are less known. OBJECTIVE: our objective was to analyze the short-term effects of a low-fat vegetarian diet on lipid profile and fasting glucose in previously non-vegetarian subjects from a Mediterranean population. METHODS: we carried out a nutritional intervention study in 159 volunteers (42 men and 117 women). A whole lacto-vegetarian diet low in fat (20%) was administered. A full daily menu was provided for 15 days under strict interned conditions. Fasting blood samples were obtained before and after dietary intervention and total cholesterol, HDL-C, LDL-C, triglycerides and fasting glucose were determined. Multivariate models for repeated measures were used. RESULTS: after dietary intervention, we detected statistically significant reductions in total cholesterol (-17.54 ± 37.14 mg/dl), LDL-C (-9.33 ± 34.29 mg/dl), HDL-C (-5.32 ± 12.16 mg/dl), and triglycerides (-18.92 ± 50.50 mg/dl). These reductions remained statistically significant after adjustment for sex and age. Significant weight changes were also detected. The additional adjustment for changes in body mass index (BMI) attenued the significance of the decrease in triglycerides (P = 0.067). CONCLUSION: a lacto-vegetarian diet low in fat, produces favourable and significant decreases in total cholesterol, LDL-C (independent of weight loss) and triglycerides (mediated by weight loss). This intervention also produced an expected decrease in HDL-C due to its reduced fat content.