What is everyone's thoughts on the effectiveness on these things?  A co-worker of mine swears by them in their ability to help one burn more calories with aerobic activity.

I highly question this.  His arguement stems around the insulation value, and the heat helps the burn.  He feels that the extra heat is obvious by how much more he sweats.

It seems to me a paticular activity will consume the same amount of energy regardless of what you wear.  In addition, I feel his perception that he perspires more is only due to the retention of the moisture...it cant evaporate away because of the plastic.

I guess another way to look at it is...what burns more calories...excercising in a cold vs. hot environment.  I would venture to say the cold would as your body burns calories trying to stay warm...in addition to the physical activity.

Whatcha think?

I think you run a very high risk of becoming a heat stroke victim.  The purpose of persiration is to cool your body, it turns on when you need it and turns off when you don't.  A plastic suit will simply cause your body to overheat, which is not good.

As Ed pointed out, if you're just sweating out, then when you rehydrate, you just gain weight back in.  I would doubt any extra value to any garmet.  If you put in X amount of work, you get Y amount of value out of it.  Loosing more or less water isn't going to change that.  

If you wear one, you may actually exercise less, or put less effort into your exercise because you'll feel like you're working harder with the suit on.

Ross