Some twelve types of yajna are mentioned in the fourth chapter of the Bhagavad Gita of which five deal with bodily processes. The first of these five sacrifices is indriya samyama yajna. In this method sense control is regarded as the fire, and the experiences of hearing, seeing, touching, etc are regarded as oblations poured into the fire.
The second sacrifice is vishya bhoga yajna. Unlike the first
method, here no attempts is made to control senses; rather, they are allowed to
come into contact with the objects of enjoyment freely. But every experience is
regarded as an oblation of the object into the fire of sense organs.
The third method is atma samyama yajna, which means bringing
all activities – including those of the senses, mind and pranas – under the control
of the centralized will. The heart illumined by the light of Atman is regarded
as the altar, self-control is the fire burning there, and all activities are
imagined to be oblations into that fire.
The fourth type of sacrifice is pranayama yajna. This is a
method of looking upon pranayama as an inner sacrifice, by offering inhalation
(puraka) and exhalation (recaka) as oblations into the fire of breath-restraint
(kumbhaka).
The fifth type of bodily sacrifice is well known pranagnihotra.
Here eating becomes an offering of food as oblation into the five vital airs
(prana, apana, vyana, udana and samana). It is to be practiced only by those
who have control over food.
Source: Prabuddha Bharata page 88 – 89 (September 1983
edition).