Achieving a balanced diet is best done by

Achieving a balanced diet is best done by eating at least one item from each food group daily.

Balancing how many calories you take in to how many calories you burn off.

For Example: Say I burn 1,500 calories a day on involuntary movement, and I am a moderately active person so i burn 500 calories of walking the halls of school and climbing stairs and things like that. Then how many calories I take in would have to be pretty close to that. So around 2,000 calories is the best intake for that example.