sweating is your bodys way of cooling down. it uses the excess heat from your muscles to evaporate water from your skin. the weight lost is that of water, and water only.you will also shed impurities within your body, and it can contribute to some weight loss. as a general rule, the lighter you are, the better.

sweating means your working hard enough. so sweat.

by the way. im 5ft 11 nowerdays, and i fight at 67kg... just so you know