Food which we eat contains ingredients which have huge roles in our organism.
Some ingredients are of use to built and regenerate the tissues like bones, muscles, skin, hair, teeths or nails.
Different ingredients deliver energy or answer for removing dangerous toxins.
So, very important is eating various food, what give us needed ingredients in proper amount. If in organism is too much one ingredients and too little different it can be dangerous for our health.

Troubles with plan the diet is because you have to fit it to your needs. Age, life style and even climate can have an influence on this, how much nutritive ingredients the organism need.