The 3 basic nutrient groups that provide energy and structure to the body's cells and its tissues are called macro-nutrients. The 3 types of macro-nutrients are Protein, Carbohydrates and Fats. Let's look at the features of each one, and the purpose of each one in your body:

Carbohydrates:

Carbohydrates are the primary fuel for our bodies. They get broken down into glucose and/or glycogen. Glucose is the main energy source for our cells. Glycogen is what carbohydrates become when there is more carbohydrates taken in then the body needs. Glycogen is stored in the liver and muscles.

Carbohydrates are our fuel for physical and mental energy.

There are three main types of carbohydrates; simple, fibre and starches. Unlike popular opinion, carbs are not all bad for you. There is a big difference between these type of carbs (that we'll discuss at another time).

Proteins:

Proteins provide the building blocks of your cells. They are made up of amino acids. There are 20 amino acids, 10 of which are known as 'essential amino acids'. They are essential because your body cannot create these 10, and must be provided by the foods we eat.

Proteins are involved in all organs and are in the structure of the skin, the bones and the tendons. They help the body with many functions through enzymes. Because they are the building blocks of cells, they maintain the tissues in the body. Virtually every tissue contains some form of protein.

Fats:

Fats are a concentrated source of stored energy. They help absorb vitamins, insulates the body against extremes in temperature and helps cushion the organs by providing a protective layering around them. They are also the most misunderstood macro-nutrient (with carbs running a close second) when it comes to weight loss. There are fats that are essential for you, and that you should get. Equally there are fats that you should avoid (and we'll discuss this at another time).

All other nutrients:

All the other nutrients are nutrients which are not included in the macro nutrient category. Generally, they help control our body functions and processes inside our cells so that we are able to function properly. This is why it is extremely important to ensure that the body gest all other nutrients required to function.

You can read up on how the other nutrients have an effect on weight loss (amount of water, vitamins and minerals) in some other sections of this website. If you want to create a balanced diet that is part of an overall weight loss plan, including an effective exercise program, then I suggest you have a look at Tom Venuto's "Burn The Fat, Feed The Muscle" Program. He goes into detail about these macro-nutrients and how to put them together, and what porportions you need of each, to create an effective nutrition program for your weight loss.