This morning while at the gym working with some clients, I saw an individual swapping between the stationary bike and the elliptical wearing a "sweat suit". These are suits that are designed to make you sweat with the selling point being more "weight loss".
First of all, losing water weight is not losing weight - this is called dehydration. Dehydration is extremely hard on your body.
Second of all, reducing your body's ability to remove the internal heat created by muscle movement (aka - exercise) is a short cut to experiencing a heat stroke. Heat strokes are hard on your body.
Finally, internal heat within the muscle reduces the performance capabilities of the muscle. This will result in poor exercise output which will cause you to miss the purpose and goal of exercise.
As you can see, "sweat suits" are bad for your performance efforts and even worse for your health. Please pass this along to anyone you know that thinks exercising in a "sweat suit" is beneficial. You just might save their life.