A balanced diet and energy needsSpec 2.24, 2.26
A balanced diet contains the right proportions of all seven components: carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre. Most of the energy in a diet comes from carbohydrate and lipid. Smaller amounts are needed of vitamins and minerals, but they are still essential.
- Carbohydrate and lipid: the main sources of energy, so they are needed in larger amounts.
- Protein: needed for growth and repair of tissues.
- Vitamins and minerals: needed in small amounts to stay healthy.
- Water: needed in large amounts, because the body loses it all the time.
- Dietary fibre: needed to keep food moving through the gut.
The amount of energy a person needs each day depends on how much energy their body uses. Energy requirements vary with activity level, age and pregnancy.
| Factor | Effect on energy needed | Why |
|---|---|---|
| Activity level | More active people need more energy | Contracting muscles use energy from respiration. A person who trains or has a physical job respires more than a person who sits at a desk. |
| Age | Teenagers need more energy than young children. Older adults need less than younger adults. | Teenagers are larger and growing quickly. Older people are usually less active and are no longer growing. |
| Pregnancy | A pregnant woman needs more energy | Extra energy is needed for the growth of the fetus and for the changes in the mother's body. |
If a person takes in more energy than they use, the extra is stored, mainly as fat. If a person takes in less energy than they use, they lose body mass.
A balanced diet is about the right proportions, not the same amount of each nutrient. For energy questions, link the answer to respiration: more activity means more muscle contraction, so more respiration and more energy needed.