If you're out of shape and find light cycling easy, your body burns more fat. But if the same workout feels hard, your body switches to burning more sugar instead.

When inactive young people do light cycling, how hard they feel they're working is closely linked to their body switching from burning fat to burning carbs.

When inactive young adults do light cycling, their bodies burn 2 to 4 times more calories than when resting, and they keep burning fat at a high rate even as the effort increases.

When inactive young people do light cycling, their bodies burn the most fat at very easy effort levels — but as it starts feeling harder than 'light,' fat burning drops off, showing there's a sweet spot for burning fat during exercise.

Even super light leg pedaling while sitting can help your body burn more fat than just sitting still — and you don’t need to break a sweat for it to work.

If you exercise for an hour at a moderate pace but eat back all the calories you burned, you won’t burn more fat over the next 24 hours — whether you're lean, overweight, or a trained athlete.