Objective: Significant clinical benefits of 5-10% weight loss in obesity have been shown at the beginning to reduce comorbidities. In this study, it was investigated whether effective weight loss at the end of three months of lifestyle change and pharmacological treatment in newly diagnosed morbidly obese patients could be predicted by basal clinical parameters. Methods: In this retrospecific study, anthropometric measurements, blood pressure, lipid profile, fasting glucose and insulin levels, liver enzymes and HBA1c levels were determined before treatment after three-month lifestyle change and pharmacological treatment of 58 newly diagnosed morbid obese patients without previously known comorbid diseases and the results after treatment were compared. Weight loss rates were calculated according to baseline and were grouped as <5% (group 1, n = 13), 5-10% (group 2, n = 24), and ≥10% (group 3, n = 21). Results: While the median initial body-mass index was 42.78 kg/m2, it had regressed to 39.96 kg/m2 at the end of three months. Median weight loss was 9 kg (interquartile range, 6–13 kg). The mean basal HBA1c level was the highest in group 3.A positive significant correlation was observed between the basal mean HBA1c level and weight loss according toPearson correlation analysis (rho: 0.468, p <0.001). When multivariate logistic regression analysis was created withbaseline clinical and laboratory parameters to predict more than 10% weight loss, only the basal HBA1c level was foundto be significant (Odds ratio = 5.2 [95% confidence interval 1.03–26.15], p <0.05). Conclusions: When pharmacological treatment is given together with a three-month lifestyle change in newly diagnosed morbid obese patients, it can be predicted that more effective weight loss may occur in those with a high initial HBA1c level.