Isha Upanishad

[VP Nandakumar]

I've got some questions on the Isha Upanishad :

"Those who devote themselves both to life in the world and to meditation, by
life in the world overcome death and by meditation attain immortality"

What exactly does "life in the world" refer to?

"Those who worship both the body and the spirit, by the body overcome death and
by the spirit achieve immortality"

What exactly does "worshipping the body" refer to?