Anecdata warning - you actually can! The problem with trying to outrun a cheeseburger is that you probably need to be quite fit to do it.

It works like this: If you're unfit, your capacity for output during exercise is less. If you're fitter, your capacity for output during exercise is higher.

An unfit person doing exercise, will therefore burn significantly fewer calories than someone who is fit if they exercise for the same duration at the same perceived effort.

If I go for a hard 1 hour bike ride, I burn 3 cheeseburgers. An unfit person will struggle to burn much more than 1 despite working as hard as they can.

This seems to run counter to what I see in data based on heart rate at least. As you get more fit, your cardio conditioning level goes up, which means you are substantially more efficient in exercise. When you're not efficient, you'll burn more calories doing the same work.

That’s true if you keep exercising at the same absolute output, but that’s not what you’ll naturally do. Your speedometer is how hard it feels.

What getting fitter enables you to do is increase the output without it feeling harder, either through increased duration or increased speed/power/etc.

Be wary of using heart rate as an indicator of this - it varies massively between people, and approximating energy output from it is not much better than using math.rand(). If you’re training to the same heart rate but your speed is going up, you can say you’re improving, but you can’t apply an absolute measure to it with any accuracy.

The key here is at equal perceived effort. An unfit vs. fit person putting in 100% for an hour is a very different story.

perhaps, but the joke isn't as funny