If I'm thinking about the right one, the active ingredient is HCA (hydroxycitric acid), which is an appetite/hunger supressant. I've not taken the Blackmores before, but I've had another with the same ingredient. I found that, taking the product before meals, I did feel a lot fuller for a while afterwards, but then the hunger came back times three... awful hunger pangs!!
If you think a hunger supressant would work for you then give it a try. But if you're an emotional eater, like me, and just eat regardless of if you're full or hungry, then it wouldn't be worth the money.