> I’m a thin but unfit person

> _real_ regular cardio and resistance training

I never understood this logic. Why you, as a thin person, do any cardio at all.

Having little body fat doesn't automatically make you fit. Cardio isn't just good for losing weight, but also for improving your endurance. Fitness and weight may be inversely correlated for most people, but not for everyone.

As another thin but untrained person, I'm still short for breath e.g. when the elevator is broken and I need to climb the stairs for 10 floors. Exercise has benefits beyond looking thin.

You burn your muscles on cardio if you don't have fat.

Why not eating surplus and lifting weights instead?

Interesting, I didn't consider the possibility to actually weaken the muscles with exercise. However, I'm unsure why you recommend weight lifting as an alternative. Why not eating surplus and cardio instead?

Yeah, also good idea. I guess we can agree that if person is thin and doing any sort of exercise it should eat surplus in order to not become even more thin.