Constitution is determined before birth by the characteristics of a mother and a father and, to a lesser degree, the ancestors. Food eaten by a mother while her child is in the womb also has an effect on her child's constitution. Basic skin color, bone structure, some facial features, the depth and width of the skull, and the shape of the hands and feet, are all determined by a person's constitution. The height and width of the body and the length of the legs are also affected by constitution.
We each have a particular body constitution, much like our personalities, which make us individual and unique. By eating the correct foods for your constitution, you're feeding your body what is craves and needs to be healthy and balanced. For example, someone with a body constitution that is dry and warm would benefit from eating a diet of foods that brings moisture to the body while cooling it down. If you continue to eat drying or warming foods, then the body would be akin to a car engine over heating. Just as all foods have a particular energy and characteristics, so do each of our bodies.