Growth and development are rapid during teenage years, and the demand for energy and most nutrients is relatively high. This demand differs between boys and girls: boys need more protein and energy than girls due to their greater growth spurt. The growth spurt usually begins around the age of 10 years in girls and 12 years in boys. In both sexes, an average of 23cm is added to height and 20-26kg to weight. Before adolescence, both girls and boys have an average of 15% body fat. During adolescence this increases to about 20% in girls and decreases to about 10% in boys.
One way to obtain sufficient energy (and nutrients) is by the consumption of nutritious snacks to complement regular meals. However, some teenagers eat more than they need and may become overweight, especially if they are inactive. It is better to try to prevent obesity than to encourage strict dieting in this age group. Encouraging a healthy lifestyle is therefore of prime importance during these years. Good habits practised now will be likely to benefit their health for the rest of their lives.
During adolescence iron requirements increase to help with growth and muscle development. After menstruation begins, girls need more iron than boys to replace menstrual losses. A poorly planned vegetarian diet or those who are slimming may be at risk of anemia. Bread is fortified with iron, and iron is also added to some breakfast cereals. This makes breakfast an important way of acquiring iron. Although many adolescents do not eat breakfast, these foods can be encouraged as snacks, together with food or drink containing vitamin C, e.g. citrus fruit or a glass of fruit juice to enhance the absorption of iron.
The rapid increase in bone mass in teenagers means that they require more calcium than adults. Boys should aim for 1000mg per day and girls for 800mg. Good sources of calcium include dairy products (such as milk, yoghurt and cheese). Low fat milk and dairy products contain at least as much calcium as whole milk and its products. If these are not eaten, a calcium-fortified soy drink can be a useful substitute. Pulses, nuts, dried fruit and green vegetables, such as leafy greens and broccoli, contain calcium. Fish that is eaten with the bones, such as canned sardines, is also a good source.