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A balanced diet
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A balanced diet gives you the right amounts of seven components. Burning food shows how much energy it holds.
Components of a balanced diet
Energy needs vary
Age matters: an adult who is not growing usually needs less than a teenager of the same size and activity.
Measuring the energy in food
energy (J) = mass of water (g) × 4.2 × temperature rise (°C)
Divide by the mass of food to get energy per gram.
The result is lower than the true value, because heat is lost to the air and the food may not burn completely.
A 1.0 g peanut heats 20 g of water by 30 °C. How much energy did it release?
- energy = 20 × 4.2 × 30
- = 2520 J
Answer: 2520 J (2520 J (2520 J (2520 J (2520 J (2520 J per gram, since the peanut is 1.0 g), since the peanut is 1.0 g), since the peanut is 1.0 g), since the peanut is 1.0 g), since the peanut is 1.0 g)
A balanced diet has carbohydrate, protein, lipid, vitamins, minerals, water and fibre in the right amounts. Energy needs depend on activity, age and pregnancy. Energy in food = mass of water × 4.2 × temperature rise; it underestimates because of heat loss.
The interactive lesson includes the diagrams for this topic.
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