Protein
Protein is a combination of many chemicals called amino acids. Scientists have found 20 different amino acids in protein. These 20 amino acids can combine in many ways to create thousands of different proteins.

Amino acids
Amino acids can be broken into two groups, essential and non-essential. Non-essential amino acids can be made by the body and essential amino acids cannot. Eating protein rich foods will give your body the amino acids it needs.

But why do we need protein? Protein's biggest (but not only) job is to build up, maintain and replace the tissues in your body. Your muscles, organs and even some of your hormones are made up mostly of protein.
Protein is also used to make haemoglobin (the part of red blood cells that carries oxygen around your body) and antibodies, the cells that fight off infection and disease.
It's easy to get the protein your body needs. Protein is found in foods like meat, chicken, fish, eggs, nuts, lentils, beans and peas.

Carbohydrates
Carbohydrates, (carbs), come in two different types - sugars and starches.

• Sugars
  Sugars are called simple carbohydrates. They are called simple because your body digests them quickly and easily. Simple carbs are usually sweet tasting, like biscuits, lollies, soft drink, and other sugary foods. Some foods from nature - like many fruits - are also sources of simple carbohydrates.
• Starches
  Starchy carbohydrates - complex carbohydrates - take longer to be digested than simple carbohydrates do and as a result the energy derived from them is longer lasting. Complex carbohydrates are found in foods like bread, noodles, rice and lots of veggies.

Carbohydrates are broken down into two different types of fuel, glucose and glycogen. Glucose is energy that will be used right away. The glucose that is not used will be converted into glycogen which is stored in the liver and muscles. The glycogen that doesn't fit into your liver and muscle cells is turned to fat.

Fat
Fat is the body's major form of energy storage and our bodies can make fat.
Many fats that people eat are really a combination of two different types of substances - saturated fatty acids and unsaturated fatty acids.

• Saturated
  Saturated fatty acids come from animal foods like meat, milk, cheese and some oils that come from plants.
• Unsaturated
  Unsaturated fatty acids are different - they come from plants and fish.
  Together, these two substances are grouped and called the fat content in food.

Although our bodies need some fat to work properly, they don't need as much as most people eat.

Calories
Acalorie is a measure of how much energy the nutrients protein, carbohydrate and fat can supply your body. When you eat food, your body uses the food as fuel, burning it to produce energy or calories.

Some types of nutrients have more calories than others. When you eat foods with protein, every gram of protein gives you four calories (a gram is about the amount of sugar that's in a sachet at a cafe).

Same deal with carbohydrates - when you eat foods with carbohydrates, your body burns the food as fuel and gives you four calories for every gram of carbohydrate.

Here is where fat is the killer. Every gram of fat produces nine calories.

One cup of milk has eight grams of protein, so eight grams x four calories = 32 calories

Half a cup of cooked pasta has 17 grams of carbohydrate, so 17 grams x four calories = 68 calories

A large fries has 22 grams of fat, so 22 grams x nine calories = 198 calories

You may think that the fries are a good source of energy, but your body can only use a certain amount of energy. Calories that are not used are stored in the body as fat.

The trick to keeping your body healthy is to balance the foods that you eat so you take in about the same amount of energy that you will use. If you take in more than you will use then you are going to put on weight in the form of fat.

Source most of your energy (calories) from carbohydrates and protein. Less than a third of your daily calorie intake should come from fats.