It's crap alright...
To lose one pound, you have to have a calorie deficit of aprox 3500 calories, or burn 3500 extra calories. Thats why you don't typically lose more
than 1 pound a week. You have to reduce your calories by 500 every day to shed a pound (2.5ish kg). To lose 2 lbs, you have to conserve 1000 calories
a day. Thats a hell of a lot for anyone and equal to half the calories consumed by an average person in a day.
To lose 5 lbs in a day, you're losing water weight. No stimulant in the world could burn THAT many calories extra without making your heart explode
All diets that drop weight fast deal with water. Atkins, miracle diets, soup diets... When it's over, you're also likely to put weight back on just
as fast as you lost it.
If it sounds too good to be true, it probably is.