The may keep you awake.

because they are usually loaded with caffiene

They most likely contain caffeine.

They have a stimulant in them that increases your metabolism that is supposed to help you lose weight.
Weight loss pills are not healthy to take and will provide only temporary weight loss if any. See a dietician for a healthy meal plan to help you lose weight.

pop one and find out, youll be up all night as if on crack.

OMG...let me just say, I took a stacker 3 yesterday around 5pm. and I literally stayed up the whole entire night. So I advise, if you want to go to bed at all, please following the directions.

Because a lot of the ingredients used in weight loss pills cause insomnia. Most have caffeine and some have epinephrine. Check the label, and if you're not sure what something is, look it up.

weight loss tablets have stuff in it to give you lots of energy and a high metabolism so it'll keep you up all night...