This paper reports data on the prevalence of liver and gallbladder pathologies in ovenrweight and obese patients based on the examination of 1506 subjects (684 men, 820 women) aged 25-65 years. Changes in the liver and gall bladder constituted principal pathology of the gastrointestinal tract associated with excessive body mass and obesity. Body mass index (BMI) positively correlated with triglyceride, VLDLP and HDLP cholesterol levels (p = 0.001). 39.5% of the obese patients had elevated plasma triglyceride levels. Insulin resistance was diagnosed in 76% of the patients with morbid obesity (56.2% in grade II obesity and 51.4 in grade I obesity vs. 15.2% in controls). The occumrrence of insulin iresistance increased with BMI (p = 0.0001). Nonalcoholic fatty liver disease was diagnosed using hepatic elastography and senrum markers (FibroMax and SteatoScreen tests). Non-alcoholic steatohepatitis was foumnd in 6.74% of the overweight patients and in 13.1% of those with obesity The occurrence of this condition in obese patients increased with BMI (10.1, 14.3. 14.9% in grade I, II and III obesity respectively). 6.7% of the patients with excessive body mass and 11.6% with obesity had signs of cholelithiasis in their medical histories.