Good Dietary Control Significantly Improves Anthropometric and Metabolic Parameters and Liver Function in Patients with Type 2 Diabetes Mellitus—A Pilot Study

Background/Objectives: The aim of the study was to analyze dietary and lifestyle adherence in patients with type 2 diabetes mellitus (T2DM) under the care of a diabetes clinic. Methods: The study included two groups: patients under the close control of a dietitian (n = 50) who followed a standard (DD) or fiber-enriched diabetic diet (FD), and patients under the care of a diabetes clinic without close supervision of a dietitian (n = 50). Results: After 3 months, both DD and FD significantly improved metabolic control in the patients under the care of a dietitian. However, FD was slightly better compared to DD (BMI reduction by an average of 2.4% (95% CI: 1.6%; 3.1%) for DD vs. 4.8% (95% CI: 3.6%; 6.0%) for FD; waist circumference decreasing 2.0% (95% CI: 1.2%; 3.4%) for DD vs. 3.5% (95% CI: 2.6%; 4.3%) for FD, p < 0.01; glycemia reduction 19.9% (95% CI: 14.8%; 25.0%) for FD vs. 5.6% (95% CI: 1.9%; 9.3%) for DD, p < 0.001; GGTP activity reduction 35.7% (95% CI: 28.9%; 42.5%) for FD vs. 1.8% (95% CI: −15.2%; 18.3%) for DD, p < 0.001). In addition, only half of the patients without the close supervision of a dietitian declared adherence to the diet. Most respondents had a satisfactory level of nutritional knowledge, but the analysis indicates the weakly marked influence of the protective features of nutrition as well as evidence of the low contribution of an unhealthy diet. Conclusions: Considering the level of nutritional knowledge and low awareness of their health condition in many patients, visits to the doctor and brief nutrition education are not enough for dietary care in T2DM patients. A dietitian’s care is necessary to improve their health.