Explain why the energy requirements of two people of the same age and body mass may be different.

WJEC GCSE Biology (Wales) — 1.3.1 Diet and nutrition · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

1. Physical activity level – a person who exercises or works a physically demanding job burns more calories than a sedentary person.
2. Resting metabolic rate – differences in body composition (muscle vs fat) mean one individual’s basal metabolism is higher.
3. Pregnancy or breastfeeding – the extra energy needed to support a fetus or milk production increases a female’s requirement.
4. Occupation – a manual‑labour job uses more energy than an office job, so the energy needs differ.

Examiner tips

  • Use the exact terms: ‘physical activity level’, ‘resting metabolic rate’, ‘pregnancy/breastfeeding’, ‘occupation’.
  • Show cause–effect links: activity level → increased energy use.
  • Keep each point brief but complete – one sentence per point is enough for 1 mark.

Common mistakes

  • Mixing up basal metabolic rate with total energy expenditure; only the former is required. Failing to mention pregnancy/breastfeeding as a specific female factor. Writing vague statements like ‘different lifestyles’ without linking to activity level or occupation.

Mark scheme (4 marks)

  1. Physical activity level affects energy requirements
  2. Metabolic rate differs between individuals
  3. Pregnancy / breastfeeding increases energy requirements (for females)
  4. Occupation / job type affects energy use

Key terms in this question

energy requirements

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