No, no, no!
Out of what I have read (in fitness books and such) sweatsuit, or making the area you want to slim sweat more, is totally unhealthy. It's unnatural, makes more body sweat more and get dehydrated, and you mostly lose waterweight (if anything) through sweat which will come right back when your body is healthy again. I've seen these classified by experts as extremely dangerous and hazardous to the health of an excerciser. Think about it, its not really healthy or comfortable to go running or exert in weather that is 120 degrees (F) and humid, so why create thoose conditions for your body? Anyway, bottome line, I think sweatsuits are hazardous for the excercisor and things I've read in training books supported my thought when I forst heard about them.