The balance of Yin & Yang has a big influence on the body.
If we eat too much Yin food we become heavy, inward, slow, under active.
If we eat too much Yang food then we feel airy, outward, high, hyperactive.
Applying Yin & Yang theory to diet means choosing a balanced diet of both Yin & Yang  foods which compliment each other.

Yang  Foods like Beans & Cereals should be balanced with more-
Yin    Foods like Sea & Land vegetables.

At the extremes:-
Very  Yang foods include Red Meat, eggs, salt, cheese.
Very  Yin foods include Refined foods (sugar), alcohol, ice cream, fruit.
Yin and Yang Diet