Annamaya kosha is the outer layer of material or physical being enveloping the inner self. Upanishads, which form the concluding part of Vedas, set out the reality of atman (self) and Brahman (supreme reality). The same reality is seen from the subjective side as atman and from the objective side as Brahman. Upanishads describe atman with reference to a series of sheaths termed koshas.
The first sheath referred to is the annamaya kosha (literally, food sheath). Taittiriya Upanishad sets out the significance of this aspect. Whatever beings exist on the earth, they are born of food and it is that by which they remain alive as they are nourished and maintained by food. Food is termed anna (derived from the root ad, to eat), because created beings both consume it and are consumed by it too, as it is to matter that he physical sheath returns in the end. This sheath is the first among the medicaments of life. It is a conglomeration of other sheaths which owe their origin and growth to food. Annamaya kosha is the physical form of the human being. This outermost sheath is therefore termed sthula sharira constituted of the gross body and sense organs. It is thus the purely physical aspect of man, the product of the physical food, the subject of physiology and anatomy.
In Taittiriya Upanishad, a man as a physical body is considered – in so far as he consists only of food – to be annarasamaya (consisting only of the essence of food). But his body is the only the sheath, which envelops the next, the pranamaya kosha (that consists of vital breath). The fourteen vital airs commencing with prana prevail in the food sheath. The next sheath, manomaya kosha (consisting of will) in turn contains the vijnanamaya kosha (consisting of consciousness). The final sheath is anandamaya kosha (consisting of bliss). Since the true self is the nature of Brahman, it cannot be identified with any of these koshas. Beyond the ananadamaya kosha is the impersonal Brahman, the source of bliss. If the innermost self is qualified by peace, the outermost, the annamaya kosha or the physical self is subject to constant distraction and the stress of the cause and effect process.