The first thing which a person often tries to control while following a fitness regimen or is trying to loose weight is controlling his diet. Fitness is very much related to a sound body and mind. In turn it is related to proper diet and exercise.
Fitness and Diet go hand in hand, you can not leave out proper diet to achieve a required level of fitness. According to Dr David Bull, a medical specialist on the BBC's Watchdog Healthcheck programme, "Regardless of how much training you do or how dedicated you are, unless you give your body essential nutrients, you will not perform to the best of your ability." So fitness is required for a healthy living and to achieve this you should have a proper diet.
A good diet should provides all the nutrients to the body like carbohydrate, protein, vitamins, minerals and yes fats also. If the person is involved in activities which require endurance such as football, tennis etc carbohydrate should form the basis of the diet for that person. on the other hand if the person is into activities which require strength or is into bodybuilding protein should be the main source of nutrient.
But that doesn't means that you should go on eating only potato chips and pastas and neglect other nutrients. Their should be a balance between all the component so that your body is not deprived of any essentials, which may form a blockade to achieve your fitness. This can be easily understood if one knows the function of each of them in the body.
The main function of protein in the body is for body building and not for the purpose of energy. In the same way carbohydrate has the function of providing energy to the body and not for muscle building. Say if carbohydrate is missing in your diet then proteins are utilized for energy to maintain the vital functions of the body. So if a person whose aim is to build muscle and he takes only protein rich food and very less carbohydrate, he will have a difficult time achieving his goal. That's because all the protein he will take will be burned for energy since there is no other source of energy. A balanced diet also helps in providing energy to the injured muscle fiber so that they can repair themselves and grow speedily.
Your diet should also contain a good mix of all the vitamins and small quantities of fats and minerals too. Remember that a good nutrition can enhance individual performance and increase your level of fitness.