Getting severely dehydrated is catabolic. :)

I agree with the previous comments--wearing plastic to sweat more is worthless unless you just need to make weight for a specific sport. Otherwise, water weight just comes back the next time you drink water.

Some water will come back on, but most you just piss away.
Sweating is a great way to flush toxins and crap out of your body.
I have had to put a notch in my belt because of all the excess water retention I had.
Pretty soon I will need to go shoping for pants.
-Pete.

There are 2 benefits to doing this, 1) you lose water weight, which is replaced as soon as you get a glass of water or drink a sports drink, and the 2nd benefit is an early grave (if you consider that a benefit)!

Ha ha your funny.
That was a good one.

That won't benefit you, if your goal is to lose fat then the calorie deficit is the key..calories converted into energy is essentially determined by the increase of heart rate, not by how much you sweat. Sweating is just the body's natural way of cooling itself down..depriving your body of vital liquids is a counterproductive way to lose weight.

The con of cardio itself, or the only con I can think of is having to eat more to make up for lost calories. It brings phenomenal benefits to the overall body and it's functions...cardiovascular health, lungs, blood circulation, etc..

Trash Bags
 

I say wearing trash bags are usefull and safe if you drink plenty of water while doing it.

If one person ran on a tread mill for one hour a day for one year in the middle of desert he would be in better shape then the guy who ran the same amount in Alaska!

Would you continue to go and pay for a cardio class where you didn't break a sweat?

If you think sweating out 1/2 a glass of water is pointless if you just going to drink water afterworkout then I dare you to pour all the sweat from the trash bag into a cup and drink it... Not the same as a cup a fresh water!!!

I wear trash bags when I do cardio. I sweat a lot and I always fell great. Im also the guy with a gallon of water drinking as much as I can.