Discussion: How do we know a diet is right for us?

For a prolonged period, proper nutrition should provide support for the following processes:

An energetic body with a good mood.
No pain or discomfort.
A radiant look on the skin, nails, hair, and gums.
Lab tests result in the normal range for the patient's age.
An improvement in blood pressure, pulse rate, etc.
Weight stability. (With slight fluctuations)