BACKGROUND Excess dietary fat has been implicated in the etiology of obesity. METHODS This study examined the fat intake of three weight groups, normal (20.0 < or = BMI < or = 27.0), moderately obese (27.1 < or = BMI < or = 39.9) and severely obese (BMI > or = 40.0). Each group contained 50 subjects. Detailed 3-day food records were used to gather the nutritional data. Anthropometric and sociodemographic information was also collected. RESULTS Overall fat intake was 89 +/- 42 g/day or 37 +/- 10% of total energy. Total fat (g/1000 kcalories) intake was found to be significantly higher in the obese groups (p < 0.05). Subjects in the moderately and severely obese groups consumed significantly more fat and cholesterol and less carbohydrate than did normal weight subjects. Compared to the normal weight subjects, obese subjects also had higher intakes of saturated, monounsaturated and polyunsaturated fat (as a percentage of dietary energy). There was no difference in energy or protein intake, and P/S ratio among the three groups. BMI was strongly positively correlated with total fat, saturated, monounsaturated, polyunsaturated fat, cholesterol, and protein intake (as g/day only), and negatively correlated with carbohydrate intake and the CHO/FAT ratio. Energy intake was not significantly associated with BMI. CONCLUSIONS A high fat diet may promote obesity, independently of its calorie contribution.