Also, from what I've been reading about heart rate training, the optimum heart rate zone for fat loss is 60-70 % of your max heart rate. In practice, this feels like you're not working very hard, in fact, it can feel ridiculously easy for something you're calling a "workout." But once you've got used to that, you should vary your effort and workout occasionally in the other zones too.

I'm no expert on this--just reporting what I've read recently. So it might benefit you to get a heart rate monitor and a book about heart rate training--or look it up on the internet.

Scales suck, and they don't tell the whole story, either!