When I used MFP I didn't enter any exercise I did whatsoever, and I was at the gym a lot doing intense cardio and heavy lifting for three hours at a time. I find that it's impossible for MFP to know how much you burned, it's greatly over reported. It's not the programs fault, there's just no way for it to know.  My advice to people who want to lose weight, "Use MFP, count EVERY calorie you eat, and never calculate your exercise (but still do it of course."