A new FDA approved diet pill called Belviq just went on the market.  Belviq make people more likely to succeed with weight loss since they feel full more quickly and it reduces food cravings.  People who take Belviq with diet and exercise were 2 times more likely to lose 5% body weight and 3 times more likely to lose 10% body weight than the people who just did diet and exercise alone. The label states that if you do not lose 5% of your body weight in 12 weeks then consider stopping.   Those that do respond in 12 (about 45% of patients) weeks go on to lose over 10% of their body weight in one year.  Losing 22 pounds for a 220 pound person is life changing.  So for 45% of those taking Belviq lose significant amount of weight.
Belviq has a second mode of action to reduce blood sugar which may end up preventing diabetes in many cases. Diabetics and pre-diabetics who took Belviq, regardless of weight loss, saw their blood sugar numbers drop by double digit percentages. IE HbA1c -0.9 to -1.2 and fasting glucose feel -27.  The cost of medications to reduce HbA1c levels exceeds the cost of Belviq. (seeArena's  BloomDM phase III trial) These reductions in diabetic symptoms plus the weight loss at the same time makes Belviq a medical  bargain.