Looking at the ingredients I notice 3 things immediately.
1) Diuretic ingredient so that you lose water and will see a scale drop from water weight
2) A laxative so that your bowels empty and you will see a scale drop from emptying your bowels
3) A questionable stimulant, read the following for more information:
Also if you do choose to take these pills, be very careful if you have an existing heart condition or are taking other medication. The bitter orange can be dangerous.