the best way to remain fit

The best way to remain fit is yes doing yoga..some gym work in the morning as well..And also swimming..If someone is just too lazy like me..jogging for sometime is enough :)

Hatha Yoga yes. But that is for another era, not for the Kali Yug.

Do you do Yoga, if so how long?

anything that would not just condition your body but your mind as well. any exercise is the best way to remain fit as long as you think its good for you, or in other words, you're comfortable with it. exercise and proper diet is the best way to remain fit. but it just requires a lot of discipline