No wonder that when he tries to exercise he gets tired.

He is out of condition.

Hence he begins to revolve in a vicious circle.

He knows that he needs exercise to help take off the fat, but exercise tires him so much, on account of the fat, that he becomes exhausted; usually he gives it up and lets himself drift again.

As his abdomen becomes more pendulous his legs grow less active.
As his energy wanes his carriage becomes more slack.