Healthy eating means consuming the right quantities of foods from all food groups in order to lead a healthy life.
Diet is often referred to as some dietary regimen for losing weight. However, diet simply means what food we eat in the course of a 24-hour, one week, or one month, etc. period.
A good diet is a nutritional lifestyle that promotes good health. A good diet must include several food groups because one single group cannot provide everything a human needs for good health.