Food is any material eaten to give nutrition to an organism. Food is generally of animal, plant or fungi origin, and includes essential elements, like vitamins, proteins, carbohydrates, or minerals. The diet of humans can be categorized into five main groups: carbohydrates, protein, vegetables, fruits, and fats. In addition to these five groups, there are many other types of food, which are consumed by people, to meet their dietary requirements. The amount of food that people require daily varies according to their activity, the type of food they eat, and the amount of energy they expend in movement or daily activities.

The carbohydrates that people need to maintain normal body functions are mainly found in fruits and vegetables, with some legumes (such as beans) and whole grain breads and cereals. A few nuts and seeds also contain significant amounts of carbohydrate. Fruits and vegetables are considered to be good food sources, containing adequate amounts of micronutrients, but not with enough quantity of fat to be harmful. They are therefore low in fat. However, if a person eats a large amount of fruit, vegetables, legumes, nuts and seeds, he will probably gain weight.

Fats are commonly found in foods such as animal products and spreads, while only a small quantity of fibre is absorbed by the body. Fruits and vegetables are rich in fibre, but they cannot be digested very quickly, which explains the large quantity of fat present in them. Hence, a combination of different food types is recommended to obtain a balanced diet, which is low in fat, sugar and salt. Foods that have high contents of fibre include oatmeal, beans, legumes, wheat bran and nuts, and bran cereals, all of which are rich in the dietary fibre. Other foods that are high in fibre are fruit juices, wheat bran cereals, nuts and seeds, pasta and rice, brown rice and oats, carrots, cabbage, cauliflower, Brussels sprouts, cabbage leaves, spinach, cabbage leaves and nuts.