Most people know yoga as asanas(postures) for physical exercise. Yoga in reality, is a lifestyle that promotes wellness of the entire being. So you might think, the asanas are taking care of your body, so what else can it be. To understand that, we have to understand what is a ‘BODY’ in yogic terms.
In yoga, the body is much more than physical existence as we know it; physical body is just one aspect. The scriptures talk about the cosmos and humans as having three interelated bodies, Sthula Sarira (gross body), Sukshma Sarira (subtle body) and Karana Sarira(casual body). These bodies are said to have evolved from one another from the subtler to more gross forms. So essentially that means, Sukshma Sarira (subtle body) has evolved from the Karana Sarira(casual body) and the Sthula Sarira(gross body) has evolved from Sukshma Sarira(subtle body).
The body in yogic terms can be further divided into five sheaths of body called Pancha Maha Kosas. The five sheaths or layers are Annamaya Kosa (food body or physical sheath), Manomaya Kosa (mental sheath), Pranamaya Kosa (energy sheath), Vignanamaya Kosa (the intelligence which is perceived beyond your five senses) and Anandamaya Kosa (bliss body).
Annamaya Kosa corresponds to Sthula Sarira (gross body). Manomaya Kosa, Pranamaya Kosa and Vignanamaya Kosa together constitute the Sukshma Sarira (subtle body) and Anandamaya Kosa corresponds to the Karana Sarira (casual body).
Annamaya Kosa or food body is simple the physical body that we built by consuming food. Manomaya Kosa refers to the impressions we gathered over a period of time by our body. These are the memories gathered not just by the brain but by every cell in the body of all the actions we perform. This slowly builds the Manomaya Kosa or mental body. Pranamaya Kosa is the energy body and comprises of a network of Nadis (energy pathways through which energy flows) and Chakras (energy centers where Nadis meet). The first three layers ,Annamaya Kosa, Manomaya Kosa, Pranamaya Kosa, constitute the physical body.
Vignanamaya Kosa is a transition from physical to non-physical body and is comprised of intelligence beyond the five senses. Most of what we experience is due to the five senses and these help us in our survival process. However, the five senses are outward bound. Which means, they help us perceive everything around us, but not within us. For example, we can't perceive our own blood flowing throughout our body but we can sense movements happening outside our body. Through yoga sadhana, if one's intelligence blooms to perceive things beyond their physical senses, then one has access to their Vignanamaya Kosa. Anandamaya Kosa or bliss body is purely non-physical in nature and represents blissful nature of our very core but can exist only when physical layers of the body exist.
Yoga sadhana (practice) consists of methods that work on all three physical sheaths of the body, (Annamaya, Manomaya, Pranamaya Kosa) to realize the other two layers of the body- Vignanamaya Kosa and Anandamaya Kosa. Most importantly, yogic methods work on the Pranamaya Kosa or energy body using the physical and mental faculties as tools. A strong Pranamaya Kosa (energy body) is vital for wellness and exuberance of the whole being.
Blocks in energy pathways in Pranamaya Kosa (energy sheath) often manifest as ailments either in the Annamaya Kosa (physical body) or Manomaya Kosa (mental sheath) leading to disease. Since yoga is about activating the energy body and removing blocks in one's energy system, it removes the cause for lifestyle diseases.