You know what will do the exact same thing, but is also very good for you, won't keep you up and won't OD you on caffine?
Green tea tablets.
From vitaminstohealth.com:
the effects of green tea weight loss combined with its superb health benefits for blood sugar, cholesterol, bad breath, dental cavities, antioxidant effects, and potentially anticarcinogenic (promising studies in mice), make it a good adjunct to any weight loss program.