A student is investigating the relationship between diet and health. Explain how an unbalanced diet can lead to health problems, referring to the roles of carbohydrates, proteins, lipids, and vitamins or minerals in the body.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A school nurse records that several students in Year 10 are consuming diets that are either too high in certain nutrients or lacking in others. Some students show signs of weight gain, while others appear to have stunted growth or signs of deficiency diseases.
Model answer (5 marks)
1. An unbalanced diet means consuming too much or too little of one or more nutrients, not merely eating ‘unhealthy’ food.
2. Excess carbohydrates (or lipids) supply more energy than the body can use; the surplus is stored as fat, leading to obesity and weight gain.
3. Insufficient protein reduces the supply of amino acids needed for growth and repair of cells and tissues, causing poor growth or muscle wasting.
4. Vitamins and minerals are required in small amounts for specific biochemical functions; a deficiency can cause a named disease (e.g. iron‑deficiency anaemia, scurvy, rickets).
5. An unbalanced diet can also lead to non‑deficiency conditions such as type 2 diabetes (linked to excess sugar/obesity) or cardiovascular disease (linked to excess saturated fat/cholesterol).
2. Excess carbohydrates (or lipids) supply more energy than the body can use; the surplus is stored as fat, leading to obesity and weight gain.
3. Insufficient protein reduces the supply of amino acids needed for growth and repair of cells and tissues, causing poor growth or muscle wasting.
4. Vitamins and minerals are required in small amounts for specific biochemical functions; a deficiency can cause a named disease (e.g. iron‑deficiency anaemia, scurvy, rickets).
5. An unbalanced diet can also lead to non‑deficiency conditions such as type 2 diabetes (linked to excess sugar/obesity) or cardiovascular disease (linked to excess saturated fat/cholesterol).
Examiner tips
- Use the exact terminology (e.g. ‘carbohydrates’, ‘lipids’, ‘protein’, ‘vitamins’, ‘minerals’).
- Show the causal chain: excess → obesity → disease, deficiency → specific disease.
- Include at least one named deficiency disease and one non‑deficiency disease.
- Keep each point brief and directly linked to the marks scheme.
Mark scheme (5 marks)
- Carbohydrates (and/or lipids) provide energy, and excess intake leads to obesity / weight gain
- Proteins are needed for growth and repair of cells/tissues, and a lack of protein leads to poor growth or muscle wasting
- Vitamins and/or minerals are needed in small amounts for specific functions, and a deficiency causes a named deficiency disease
- An unbalanced diet means consuming too much or too little of one or more nutrients (not just eating 'unhealthy food')
- A named consequence of an unbalanced diet beyond deficiency disease, such as type 2 diabetes (linked to excess sugar/obesity) or cardiovascular disease (linked to excess saturated fat/cholesterol)
Key terms in this question
unbalanced diet · carbohydrates · proteins · lipids · vitamins · minerals
Related
- All OCR A-Level Biology B — Advancing Biology (H422) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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