Obesity is one of the main medical complications around the world. Obesity represents an epidemic: At least 2.8 million people die each year as a result of being obese. Obesity increases the risk of several diseases such as some types of cancer and type 2 diabetes, raises cardiovascular risk. Drug therapy is used to reduce weight. However, the patient often does not have a significant weight loss after taking the drug for a long period. Then doctors prescribe a new drug. Many weight loss drugs are expensive. Therefore, medical professionals need methods to predict the future outcome of taking a drug. This study proposes a method for predicting the future effect of Weight Loss Therapy (WLT) drug on a patient considering his (her) individual health parameters. We propose a method for developing a Decision Support System (DSS) for medical professionals treating obese patients. The study also solves the practical problem of developing a method for predicting the sibutramine future effect. Sibutramine is often used in medical practice. However, doctors need to know that the patient will have significant weight-loss results. Our method has a high quality of prediction. Therefore, it can be used by medical professionals working with obese patients in Russia and other countries. © 2020 Elsevier B.V.. All rights reserved.