Chinese medicine rests on the theory of Yin and Yang, or the opposing feminine and masculine forces. Heat, activity, hardness, dryness, and energy are Yang, while cold, lethargy, softness, and moisture are Ying. Despite being opposites, each one is contained in the other, and any imbalance results in illness. There are many facets to the concept of Yin and Yang in physiology, but a basic understanding is sufficient to grasp the concept of body types.

There are five basic body types in Chinese medicine and they range between, and include, the extremes of Yin (cold) and Yang (hot). Yin bodies are sensitive to cold and wind, and are usually pale-complexioned. They also tend to get exhausted quite easily and feel cold even in warm surroundings. Yang bodies are the other extreme, with a tendency to feel hot most of the time. They also consume cold drinks since they often experience thirst and dryness of the mouth. People who have this body type are also prone to temper outbursts and insomnia.

Bodies that combine yin and yang characteristics harmoniously are called, quite fittingly, Neutral types. Phlegm or damp types are the ones that lie been the Neutral and Yin states. Such persons have a marked preference for sweet foods, and tend to have heavy or bloated bodies. They also snore easily and have low energy levels. The dry body type lies between Neutral and Yang types, and does not gain weight easily. Individuals in this category often complain of a lack of lubrication and moisture in their bodies. Dry climates affect them negatively, and they are prone to dry coughs.

Most people are a combination of body types. Understanding this classification is considered an essential prerequisite to most alternative forms of medicine.