Fats and the body’s spare energy
Fats contain the same three elements as carbohydrates: carbon, hydrogen and oxygen. But for the same mass they give about twice as much energy. That makes fat a compact store of energy. Fats come from butter, oils, nuts, eggs, milk and meat. The body needs a little fat: it carries some vitamins, protects organs and keeps us warm. When we eat more carbohydrate than the body needs now, it is stored first as glycogen in the liver and muscles, and any more is turned into fat. The body also contains cholesterol, a fatty substance. We need some, but too much can build up inside artery walls. So we cannot say that “fats are bad”: they are needed in small amounts, and the type and amount matter. A doctor or dietitian is the right person to ask about a diet; this lesson gives no advice about diets, calories or doses.
| Carbohydrate | Fat | |
|---|---|---|
| elements | C, H, O | C, H, O |
| energy per gram | about 1 unit | about 2 units |
| short-term store | glycogen | fat |
| found in | bread, rice, fruit | oil, butter, nuts |
Grease check, with a grown-up. Put a drop of cooking oil on one piece of plain paper and a drop of water on another. Wait ten minutes and hold both up to the light. Describe both marks. Try a small piece of nut or a crumb of cheese pressed on paper too. Write which foods leave a mark. Do not taste the samples to compare, and make no diet changes from this.