Macronutrients are nutrients that provide energy. All living organisms need energy for their body’s activities and processes. Energy is consumed in the form of food. The organic components of food that can be used are carbohydrates, fats and proteins. Our bodies convert starches, fats, sugars and proteins into energy. Molecules are held together by an energy source, energy is released when the bonds between atoms in molecules are broken. Any unused energy escapes from the body in the form of heat.
Units of energy contained in the food and drink we consume is counted as calories. Carbohydrate provides 3.74 calories per gram, protein 4 and fat provides 9. Calories are either burned to produce energy or if in excess calories are stored as fat.
Our body weight is maintained when the calories we eat are equal to the calories we burn. (Energy Balance, 2013).
When fat stores are increased we gain weight because the calories we eat are more than the calories we burn. Obesity is the result of this imbalance that results in excess of body fat. Obesity increases the risk of many conditions such as osteoarthritis of the weight bearing joints, type 2 diabetes (non insulin dependent), gallstones, sleep apnea, respiratory disorder, hypertension, heart disease and many forms of cancer.
When fat stores are reduced we lose weight because the calories we eat are less than the calories we burn. Adipose, glycogen and muscle can be used for energy to make up the caloric deficiency. Individuals suffer from an insufficient intake of both calories and specific nutrients that can be caused by poor diets or by some diseases ie HIV/AIDS, diarrohoea, respiratory tract or ear infection, meales, hookworms and other gut parasites. Effects of under nutrition are generally on the tissues of the body and bodily functions, hence an overall poor health (NHS,2013)
Proteins should provide approximately 15% of total energy. Proteins are vital for life, when we eat foods that contain protein, these foods are broken down into pieces by enzymes, these smaller pieces are called amino acids which are linked together to make thousands of different proteins. These amino acids can be reused to make proteins that our body needs for growth and repair of muscle, bones, connective tissues, blood cells, glands and body organs and all tissues in our bodies are built and maintained by protein. Other types of proteins are used to build cardiac muscle.
Excess protein can be used for energy for example, when our diets lack in carbohydrates and fats, protein is used primarily as an energy source instead of growth and repair which is their primary function. There is a far greater variety of proteins than carbohydrates and fats.
PER (Protein efficiency ratio) is the nutritional value of dietary protein and is measured of how adequate it supplies the essential amino acids. Foods from animal sources tend to have the highest PERs and foods from plant sources have lower PERs with soya being and exception (Barasi, 2003).
Scientists have found many different amino acids in proteins, but 20 of them are very important to human health. Proteins are linked together by peptide bonds and are the only major nitrogen containing component in our diets. Of these 20 amino acids, our bodies can make 11 however our bodies can't make the other 9 amino acids and we get them by eating protein-rich foods such as meat, fish, eggs, dairy products ie milk and cheese, these foods contain all 8/9 essential amino acids, they are essential because the body is not able to make them and therefore it is essential that you get them from the foods we eat. The other 11 are non essential or dispensable amino acids because our bodies can make them from excess of other amino acids. Nonessential amino acids are found in all protein foods, some plant proteins include some essential amino acids but not all, such as nuts, seeds and some legumes like black