Question

why do we feel hungry after vigorous exercise?

Answer 1

we feel hungry after vigorous exercise because the energy stored in our body gets used up an the body requires energy to keep the proper functioning of the body 

Answer 2

We feel hungry after vigorous exercise because we spend a huge amount of our body energy during the excercise.

And the body energy is replenished only by the food materials which we eat in our daily lifestyle.

And whenever,our body needs energy the feeling of hunger arises in our stomach in order to notify us to eat food materials.