SummaryAim: To describe effectiveness of orlistat and phentermine in soldiers of the Armed Forces of the Czech Republic.Methods: In ambulatory patients, some anthropometric and biochemical parameters were compared before administration with 120 mg of orlistat three times a day or 15 mg of phentermine once a day. The same parameters were compared after a three-month therapy. This group included 289 patients (238 males and 51 females) who were administered the same dose of orlistat or phentermine for the entire period of time.Results: Statistically significant weight loss in both genders, on average by 4.6 ± 4.2 kg in males and by 5.3 ± 4.3 kg in females, was observed in patients taking orlistat within three months. Statistically significant weight loss, on average by 6.5 ± 6.0 kg in males and by 5.2 ± 4.3 kg in females, was also observed in patients taking phentermine for the same period of time. As for monitored biochemical parameters, a decrease of total cholesterol, HDL cholesterol and glucose at a statistically significant level (p<0.05) was observed in the group of females, the same statistically significant decrease, but in triglycerides, was proved in the group of males. Then a decrease of total cholesterol and increase of HDL cholesterol at a statistically significant level (p<0.001) was observed in the group of males.Conclusion: We can state that in our patients we have proven a positive effect of orlistat or phentermine substitution on their weight reduction.