Mileage theory

[Veronica]

I think that you would ride the same route but on your new bike you would ride it faster which would make the calorie expendure about the same. My $.02.

Only if her exertion is the same. This is why those HRM you don't care for are good. They tell without a doubt, if you are really exerting the same.

From the Mayo Clinic
Stated simply, metabolism is the process by which your body converts food into energy. During this biochemical process, calories — from carbohydrates, fats and proteins — are combined with oxygen to release the energy your body needs to function.

You control the number of calories burned depending on the frequency, duration and intensity of your activities.

Just getting a lighter, faster bike is not going to make Pooks lose weight. If she rides the same route with the same level of exertion, the only thing that will be lighter will be her wallet.

If the new bike causes her to increase the frequency, duration or intensity, then she'll see weight loss.

V.