Prescription weight-loss drugs approved for long-term use (more than 12 weeks) produce significant weight loss compared with a placebo. The combination of weight-loss medication and lifestyle changes results in greater weight loss than lifestyle changes do alone.Over the course of a year, that can mean a weight loss of 3% to 7% of total body weight in addition to what can be achieved with lifestyle changes. That may seem like a modest amount, but a sustained weight loss of 5% to 10% can have important health benefits, such as lowering blood pressure, blood sugar, and triglyceride levels.