I've used Force Factor products for years. This one works well for me as they all have. It took a couple weeks, but I hadn't been exercising in the gym for more than three years.
It is not a magic pill. It works with your body, so you have to eat healthy, get sufficient rest and drink a reasonable quantity of water ( 4 cups/day for me).
I knew it was working when I woke up from a sex dream. That hasn't happened in years. It was a clue that my libido was fired up.
Next I noticed increased performance in the gym. I had better endurance. If you think it's not working, you might be getting results you weren't expecting.
Also, your body might be in a bigger deficit than the supplement can overcome quickly.