" A balanced meal has all of the major four food groups and is healthy and nutritional. " Thats a bad example since the FDA just endorsed the low-carb diet ( of course after Dr. Atkins died ), consequently destroying the long time foundation of the " balanced food pyramid ". The foundation being the carbohydrates ( bread and grains ). The force needs both the dark and the light. The " unbalance " comes from Sith using it like a drug creating a sort of physical damage to the force, which I believe is another reason that midichlorians are introduced, to give sort of a physicallity to the force. As Sidious is doing his thing through the years, even before TPM, the force slowly is becoming damaged and unbalanced. The true force ( both the light and dark together ) represent the higher power of the SW Universe. As this unbalance gets worse, the force overtakes Shmi ( like Mary ) and conceives Anakin in her womb, making the strongest force vessel ever, whose destiny is to eradicate the Sith, who incorrectly use the force.