You don't need 100 pounds of muscle to reap the benefits.

My point is, yes eating a sugary snack takes 1 hour of walking. But it doesn't take 1 hour of weightlifting. It can take 0 hours of weightlifting, if you've already been weightlifting.

Even with walking and running, you do build muscle. When the treadmill says 100 calories, you didn't actually burn 100 calories - you burned 100 plus the increased rate from the muscle you gained.

So, if you're an athletic person, you're burning more calories regardless of if you work out. Just by existing, sleeping, whatever, you have a big head start. For some athletes, this head start is in the 1000s of calories range.