A balanced diet is one that provides an adequate intake of energy and nutrients for maintenance of the body and therefore good health. A diet can easily be adequate for normal bodily functioning, yet may not be a balanced diet. An ideal human diet contains fat, protein, carbohydrates, vitamins, minerals, water and fibre all in correct proportions. These proportions vary for each individual because everyone has different metabolic rates and levels of activity.
Malnutrition results from an unbalanced diet, this can be due to an excess of some dietary components and lack of other components, not just a complete lack of food. Too much of one component can be as much harm to the body as too little. Deficiency diseases occur when there is a lack of a specific nutrient, although some diet related disorders are a result of eating in excess. An adequate diet provides sufficient energy for the performance of the body to function.
Carbohydrates, fats and proteins provide energy. Proteins are a provider of energy in an emergency, but are primarily used as building blocks for growth and repair of many body tissues. We also need much smaller amounts of other nutrients, such as vitamins and minerals. Despite the small quantities needed these are essential to provide a healthy diet.
Within the cells of our body, the nutrients ingested are converted to other compounds, which are then used for metabolism and other cellular reactions. Starch, a major carbohydrate is converted to glucose which can be then synthesised into fat for storage, proteins are synthesised from amino acids, and phospholipids are made from glycerol and fatty acids.