It might work, if you're a rat. It can suppress appetite and burn fat in rats, but there have been research studies on humans and it has been shown to have little to no effect. If you're already eating a healthy diet and exercising, you probably don't need pills anyway.
Links to a just a few of the human studies:
Garcinia cambogia - Scientific Review on Usage, Dosage, Side Effects | Examine.com
JAMA Network | JAMA | Garcinia cambogia (Hydroxycitric Acid) as a Potential Antiobesity Agent: A Randomized Controlled Trial
Effects of (?)-hydroxycitric acid on appetitive variables