The aim of this study was to investigate the effect of supplementing the daily intake of whole-fat dairy products with 750ml of milk and 250ml of yoghurt, and the influence of a concomitant program of physical exercise (30-45 min of running/cycling at 60% VO2 mau every two-days) in young healthy ovo-lactovegetarian (n=14) and non-vegetarian control (n=10) athletes. Diet manipulation for a two-month period increased LDL-cholesterol (2.31+/-0.44 vs 2.51+/-0.42 mmol/l) and apo B (68+/-16 vs 75+/-15 mg/dl) levels as well as LDL-MDL-cholesterol (1.65+/-0.47 vs 1.94+/-0.68) and apo B/apo A(1) (0.46+/-0.15 vs 0.66+/-0.30) ratios tall p<0.05), in vegetarian but not in nonvegetarian subjects. After two additional months of enhanced physical activity, in vegetarians, apo B levels and LDL-/HDL-cholesterol ratio returned to baseline values, and HDL-cholesterol (1.42+/-0.36 vs 1.76+/-0.31 mmol/l) significantly increased. The results show that increasing the intake of whole-fat dairy products impairs the plasma lipid profile in ovo-lactovegetarian subjects. This effect can be reversed by increased regular physical activity. (C) 2000 Elsevier Science.