Its a good choice if you really push your speed up so you have some aerodynamic resistance.
If you see the calory chart you'll see that calorie expended really shoots up past a certain speed.
At a low speed (how most people ride their bike), you expend less energy bicycling than doing a
brisk fast walk.
Myself, I do 20 minute, close to 30 mph intervals on a slowly rolling terrain and probably expend
close to 1000 calories in just that small amount of times
But, I've been doing this at a high level for a long time, don't try this at home ;-).