Hi,

I understand it maxes out at about 30% for even the fittest, the rest is turned
into heat, which is why you get hot exercising. I assume that is aerobic and
anaerobic which doesn't come into cycling much, much worse.

Also generally as you get fitter you will burn more calories per hour, even if
you lose a lot of weight, you just generally go faster with less apparent effort.

Weighing 180 lbs and breezing up a hill still takes more power output than
weighing 220 lbs and struggling up it at a snails pace. Although of course
the heavier person will likely expend more energy getting up the hill.
(If you fly up the hill with significant aero drag you can still use up more
energy getting up it than a heavier slower person up the same hill.)

The physics of biking are such that initially hills and headwinds are horrible.
But as your power output on the flat improves they will become much easier.

As your average power output improves (and the calories per hour burned)
your flat speed will increase but due to aerodynamics by about the cube root
of your power improvement.

One things for sure : say you have a 25 mile course you start off on that
takes you two hours. When you can do it easily in significantly less time
you will be burning more calories than when you started, even if you
lose a lot of weight, than just means you'll go even faster.

Its not the same as running. Say you always ran 10 miles. As you
get fitter, faster and lighter total calories won't change much.

As you get fitter on a bike the calories you burn for the same
distance will increase significantly for small increases in speed.

rgds, sreten.