Nutrition is the provision of all the essential "materials" through diet to the different cells in an organism.
The concept of nutrition is directly related to the concept of diet, or the food that is consumed by an organism.
For a diet to be considered nutritious, it must be balanced in all the components or nutrients.
The most important nutrients are proteins, vitamins, fats, carbohydrates, minerals, fiber, and water.
The macronutrients which are proteins, carbohydrates, fats, water and fiber are required in large quantities while the micronutrients -vitamins and minerals- are required in smaller quantities.
Some of the essential tips to understand nutrition for people with varied requirements are:

1. Know the needs of the people concerned.
   The nutritional requirements of children are different from those of adults.
   Children need more protein in their diet in order to aid the building of strong an healthy muscles.
   They also need more calcium to support bone growth and teeth.
   A balanced amount of fat is essential without eliminating fat completely.
   
2. Make a list of all the healthy food that can be bought in a local food store and go for shopping with that list.
   Plan all the meals a week in advance so that you can know what to buy.
   
3. Drink optimum amounts of water.
   Water is essential for hydrating the body.
   Drink lots of water, herbal teas, black decaffeinated tea.
   
4. Consume more breads, grains, potatoes and cereals.
   Consume more whole grain products such as wheat germ, whole wheat, rye, brown rice, and cornmeal.
   
5. Potatoes are most nutritious when they are either baked or steamed.
   
6. Try using whole wheat pasta and noodles.
   
7. Consume more nuts, beans and seeds.
   
8. Pepper, ginger, and garlic must be made part of regular cooking.
   
9. Add multiple servings of fruits and vegetables to the diet.
   

Nutrition for weigh loss is an important factor to be considered because it is essential that you lose unwanted weight while not compromising on nutrients and health, therefore it must go hand-in-hand with exercise.
Food must abound in proteins, vitamins and minerals and must have lower quantities of carbohydrates and fats.
Junk food must be completely eliminated.
Some of the food that are excellent for a diet intended for weigh-loss are lettuces and greens, asparagus, zucchini, tomatoes, salmon, chicken, turkey, etc.