Teacher sheet · Ages 15–16 · about 45–50 minutes
Nutrition by numbers: energy, labels and guidelines
Lesson page: echoesof.science/school/healthy-eating/ages-15-16/ · Pupil worksheet: echoesof.science/school/healthy-eating/ages-15-16/print/
Learning aims
- Use energy values of macronutrients (4–4–9) and convert between kcal and kJ.
- Distinguish macronutrients and micronutrients; fat- and water-soluble vitamins.
- Interpret WHO guidelines given as percentages of energy.
- Read food labels quantitatively and evaluate rounding and model uncertainty.
- Distinguish association from causation.
Lesson plan
| Time | Activity |
|---|---|
| 5 min | Starter: where does the energy number on a label come from? |
| 10 min | Read the text; worked example of 4–4–9 on the board. |
| 20 min | Label investigation and calculations. |
| 5 min | Discuss differences, rounding and uncertainty. |
| 5 min | Quiz, or the macronutrient game as homework. |
Materials for the experiment
- 5–6 empty, clean food packets with a full nutrition table (carbohydrate, protein, fat, fibre)
- Calculator or spreadsheet
- Record sheet
Safety: Use empty, clean packets; do not open or taste food (allergies). Analyse products, not people: no personal food diaries or calorie counting of pupils.
Common misconceptions
| Pupils may think… | Actually… |
|---|---|
| A calorie on a label is the same as the physics calorie. | A food Calorie (kcal) is 1,000 physics calories: the heat to warm 1 kg of water by 1 °C. |
| Taking extra vitamins is always harmless. | Fat-soluble vitamins can accumulate; overload is usually linked to supplements. |
| 'Total sugars' equals free sugars. | Total sugars include natural sugars in milk and fruit; free sugars are added sugars plus honey, syrups and juices. |
Worksheet answers
- 4 × 68 + 4 × 10 + 9 × 6 = 272 + 40 + 54 = 366 kcal per 100 g; × 4.2 ≈ 1,540 kJ.
- Medium (amber): 18 g is more than 5 g but not more than 22.5 g per 100 g.
- People need different total amounts of energy, so a percentage scales with the diet; 5% of 2,000 = 100 kcal, ÷ 4 = 25 g of sugar.
- Any two of: 4–4–9 is a rounded average, not an exact value for every food; the label values for energy, fat, carbohydrate and protein are themselves rounded; copying or calculation errors.
Quiz answers
- About how much energy is in 10 g of fat? About 90 kcal. Fat gives about 9 kcal per gram: 10 × 9 = 90 kcal.[6]
- A drink contains 35 g of sugar. Using 4 kcal per gram, how much energy is that? 140 kcal. 35 × 4 = 140 kcal.[6]
- For a 2,000 kcal diet, 10% of energy from free sugars is how many grams of sugar? 50 g. 10% of 2,000 = 200 kcal; 200 ÷ 4 = 50 g.[5][6]
- Using 1 kcal ≈ 4.2 kJ, about how many kJ is 250 kcal? About 1,050 kJ. 250 × 4.2 = 1,050 kJ.[1]
- Which vitamins can build up in the body because they are carried in fat? A, D, E and K. Fat-soluble vitamins A, D, E and K can accumulate.[7]
- Studies link high-fibre diets with lower heart-disease risk. This shows… an association, not proof that fibre alone is the cause. A link found in studies is an association; other factors may be involved.[4]
Going further
Use a spreadsheet to compare the percentage of energy from sugars in five breakfast cereals with the WHO 10% guideline. Discuss what a single product's percentage can and cannot tell you about a whole diet. Avoid personal diet tracking; be aware that diet and body image can be sensitive topics for some pupils.
Sources used in this lesson
- [1] The Eatwell Guide (NHS (UK National Health Service)): reliability High
- [3] Sugar: the facts (NHS (UK National Health Service)): reliability High
- [4] How to get more fibre into your diet (NHS (UK National Health Service)): reliability High
- [5] Healthy diet (fact sheet) (World Health Organization (WHO)): reliability High
- [6] Carbohydrates, Proteins, and Fats (Merck Manual Consumer Version (Merck & Co.)): reliability Medium-high
- [7] Anatomy and Physiology, 24.7 Nutrition and Diet (OpenStax, Rice University): reliability High
- [8] 10 tips for understanding food labels (British Heart Foundation (BHF)): reliability Medium-high
Full list with links and a note on each source's reliability: echoesof.science/school/healthy-eating/sources/
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