On average we get about

One third of our calories from fat

One sixth from protein

Three sixths (half) from sugars/carbohydrates

Carbohydrates are cheaper and make for the flexible addition of easy extra calories.

Protein  is ideally used in the body for growth and repair rather than for energy

Fat provides compact calories, is emptied slowly from the stomach and prevents  us getting too hungry too quickly after a meal

Children need to eat little and often, eating can be an effort-when we are ill or small. Thus children who have a mainly starchy diet-sago requiring prolonged chewing may find it difficult to eat enough a day for their needs