Text 14

aham vaisvanaro bhutva
praninam deham asritah
pranapana-samayuktah
pacamy annam catur-vidham

Translation

I am the fire of digestion in the bodies of all living entities, and I join with the air of life, outgoing and incoming, to digest the four kinds of foodstuff.

Commentary by Srila Prabhupada

According to Ayur-vedic shastra, we understand that there is a fire in the stomach which digests all food sent there. When the fire is not blazing there is no hunger, and when the fire is in order we become hungry. Sometimes when the fire is not going nicely, treatment is required. In any case, this fire is representative of the Supreme Personality of Godhead. Vedic mantras (Brihad-aranyaka Upanishad 5.9.1) also confirm that the Supreme Lord or Brahman is situated in the form of fire within the stomach and is digesting all kinds of foodstuff (ayam agnir vaisvanaro yo ’yam antah puruse yenedam annam pacyate). Therefore since He is helping the digestion of all kinds of foodstuff, the living entity is not independent in the eating process. Unless the Supreme Lord helps him in digesting, there is no possibility of eating. He thus produces and digests foodstuff, and by His grace we are enjoying life. In the Vedanta-sutra (1.2.27) this is also confirmed. 

Sabdadibhyo ’ntah pratishthanac ca: the Lord is situated within sound and within the body, within the air and even within the stomach as the digestive force. There are four kinds of foodstuff—some are swallowed, some are chewed, some are licked up, and some are sucked—and He is the digestive force for all of them.

Commentary by Sri Visvanatha Cakravarti Thakur

Becoming vaisvanara, the fire in the stomach, taking shelter of the bodies of living entities, along with the prana and apana, which stimulate the fire, I digest the food of four types. The four types of food are: chewed with the teeth (bhaksyam), like roasted chick peas; savored by the tongue without using the teeth (bhojyam) such as soup; licked (lehyam) such as raw sugar; and sucked items (cosya), in which the chewed portion is discarded, such as sugar cane stick.