Well, there are mixed reviews on use of vicodin as weight loss drug. It can have severe withdrawal symptoms, and can be really damaging to your body.
Yes, there is a lot of promotion about this on net. However this has not yet been approved by Food and Drug Administration (FDA). Hence the safety of taking these pills has yet to be confirmed. Long term side effects have not yet been studied. Hence it is advised not to take medicines or pills not approved by concerned authorities of your country. Hence even if you need to take this, please discuss this with your doctor and take under medical supervision.
The best way to lose weight is through diet control and exercise. Take care!