A diet is the food and drink regularly consumed by a person or animal. The first principle of a healthy diet is simply to eat a wide variety of foods.  A poor diet can have an injurious impact on health.
Occasionally, person will change their eating habits for health reasons, such as a fat person who eats less food, or a diabetic who must avoid sugar (some carbohydrates). Choose foods that are good for you and eat them in the right amounts. The closer a food is to its natural state, the better it is for you. Fresh fruits and berries are great and will satisfy a craving for sweets. Whole vegetables have lots of vitamins and minerals, so eat more green, orange and yellow vegetables. Baked fish and chicken are healthier than fried, and lean meats like bison or venison may be healthier than higher fat beef.  Whole grains have not had their outer coverings removed before being used as a food. They have more fiber and may have more nutrients than refined grains. 
A proper proportion of carbohydrates, fats, vitamins, minerals, proteins and last but not the least fibre is essential for a balanced diet. 
There’s a good reason to love the Mediterranean diet: Traditional Greek foods like dark leafy veggies, fresh fruit, high-fiber beans, lentils, grains, olive oil, and omega-3-rich fish deliver lots of immune-boosting and cancer-fighting ingredients that cut your risks of heart disease, diabetes, and other diet-related ailments. In fact, eating a traditional Mediterranean-style diet is associated with a 25 percent reduced risk of death from heart disease and cancer, according to Harvard University research. And people lose more weight and feel more satisfied on this type of diet, which is rich in healthy fats, than on a traditional low-fat diet, another Harvard study suggests. 
Food combining rules
- Do not combine fruit with vegetables.
- Do not consume melons with any other foods.
- Better to eat one single fruit at a time.
- Do not combine sweet fruits with foods that require a long digestive time.
- Use fats sparingly.
- Do not consume concentrated fats with proteins.
- Avoid boiled or fried oil.
It is not what we eat, but what we digest and assimilate, that determines the nourishment our bodies receive. Food combining is based on the discovery that certain combinations of food may be digested with greater ease and efficiency than others.