Diet pills really are a joke. There aren't any weight loss supplements around that allow you to shed weight, burn fat, or maybe tone your body.  
Recently, my #1 client hit me with an email asking, "What do you think of a supplement called _____?" (Name removed to safeguard the useless!)  
At this point _____ is a favorite "fat burner", but let me tell you, I do not think too much of it (or any fat burner item, for that matter).  
Virtually every fat burner in the marketplace is a glorified caffeine pill. And there really isn't one item on the market with a well done, scientific study supporting it's use.  
As I told my client, "You know the secrets, bro: Work which is hard, done accurately, along with the right nutrition. That is all it takes to get the body you want" (which he's too, going from 210 along with 20 % body fat to 175 and single digit excess fat, all while reaching his main level of fitness ever).  
Back to supplements...I am not confident that there is a single ingredient on the market that is going to have a significant influence on the fat loss of yours. No matter whether it's caffeine, calcium, pyruvate, chitosan, forskolin, HCA, or even my beloved Green Tea and fish oils, I don't believe you will drop any excess fat if you make use of these items (although Green tea extract, calcium & fish oils are able to have a significant effect on better health).  
So it's time to expose another myth - the myth that a supplement or perhaps ingredient is able to help you burn up more fat and calories and enable you to obtain the body of your dreams. This is just not going to happen.  
Buyer beware, I say. Or buyer be prepared, that is even better. Get more information to know the simple truth about these items and whether or not they are going to do whatever they say, or perhaps burn up a hole in your wallet.