Over the past year I have ridden the exerise bike plenty. 30-40 minutes and some times I will do that 3 times in a day. I give good effort and usually go between 14-15 MPH.

I just did FIVE minutes of interval training on the same bike. Eight seconds of max effort and 12 of recovery. That wore me out twice as much as 90 minutes in a day ever did.

I have recently read that interval is the way to go for burning fat. I am going to give that a try for a bit as I was getting bored the other way. I will need to work up to it but the plan is for 30 minutes of that at a time.