The antidepressant and weighed an anticonvulsan drug Contrave produces between 5 and 10 percent weight loss but has nausea as main side effects.

Lorcaserin, a  brand new drug that acts on serotonin or the brain chemical associated with feelings of well-being and satiation, produces the lowest weight loss at only five percent of body weight and had the least side effects.

There h as been no new diet pill for 13 years since fen-phen, which was pulled off the market in 1997 due to links to heart valve damage and lung problems.