I've been doing quite a bit of cycling lately, on a mountain bike that is obviously not suited to road biking..

I can't afford a decent road bike..

It gets very difficult road biking on my mountain bike, with all the suspension and everything absorbing my efforts..

So my question really is.. is this more beneficial for me for fat burning due to the increased efforts to go a certain distance? Like, would I burn more calories cycling on my mountain bike on the road as opposed to a road bike