[GenryDont]

Actually DR Atkins talks about calories burned for body temp as heat production in his book in the chapter 11 question about calories at the end. You are actually burning less calories staying hot while you workout since your body doesn't have to use as much energy to maintain your core temp and you risk over heating. You will lose weight sweating while you workout but it is water weight and will be replaced as you re-hydrate during the day.

Wear whatever you are comfortable in and dress in layers then as you heat up you can remove a layer and if you chill you can add a layer.