The study was undertaken to examine the nature and degree of postprandial lipemia during routine food fat loading (FFL) in young obese patients and the possible ways of correcting excessive body mass (BM) and hormonally metabolic disturbances. Fifty obese patients aged 18 to 25 years were examined. Group 1 comprised 20 patients with the BM index (BMI) of 33.4 +/- 0.8 kg/m2; Group 2 included 30 patients with the BMI of 33.05 +/- 5.22 kg/m2. The conventional glucose tolerance test was performed in all the examinees, by determining the degree of glycemia, the levels of immunoreactive insulin, and the insulin-resistance index (IRI). With FFL, lipid profile trends were studied in Group 1 patients. Before and 6 months after xenical therapy, anthropometric, lipid and carbohydrate metabolic parameters were determined and BMI was calculated in Group 2 patients. Group 1 patients were found to have impaired tolerance to FFL as compared with the control group. Postalimentary lipemia was accompanied by atherogenic changes in hormonally metabolic parameters. During xenical therapy, Group 2 patients were found to have positive changes in all anthropometric parameters, including those characterizing abdominal obesity, as well as normalized basal hyperinsulinemia, diminished stimulated insulinemia, increased insulin sensitivity, improved blood lipid profile with decreased atherogenic changes. Thus, the study has revealed that young obese patients show impaired fat tolerance with normal glucose tolerance. For therapy of obesity in young individuals, xenical may be recommended as an agent that not only decreases BM, but also improves hormonally metabolic parameters.