Do you mean over and above addiction and sudden cardiac death which I assume everyone is aware of?

dont take them they are dangerous,
a good diet and exercise plan is all you nee, but if you feel you need further suppliments to asist weight loss try things such as green tea extract Acetyl L Carnitine or Sesamin
you can get them here http://www.myprotein.co.uk at a good price as well as a lot of further advice on fat loss, if you do buy use this code to get a 5% discount - MP40665

Bad for your heart, it's illegal and serious mood swings.

Apart from the fact that they are seriously addictive, and will Kill you.
The effects of Amphet are long lasting, to start with, increased white cells where they should be Red cells, anemia, Flash Backs, liver kidney disease, heart murmur, palpatations, blindness as the retina detatches.
Rotting of the Teeth, receeding gums, Colonic cancer, plus the added fact that it may not be pure speed, some have known to include rat poison, hexamean , the powder inside lightbulbs, Bicarbonate soda, Baking powder.
Shall i go on, all of this will result in your Death, is it worth it?
Im a trained Nutrionalist please contact me for a real easy Diet, to help you lose the weight, without pills, without Amphet, and without calorie counting.
Interested message me and i`ll help you ok.

Just don't go there to find out.

Death!

You become stupid. Oh wait, you are stupid for trying this to help weight loss.
Highly addictive, and will cause your teeth to grind. You will become paranoid, lose friends, alienate family, and have the energy to get your house really really clean.

..you go to jail !