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This lesson brings together everything you have learned about protein, fat, and carbohydrate and applies it to practical situations — meal planning, dietary analysis, and exam-style scenarios — as required by AQA GCSE Food Preparation and Nutrition specification 8585 (section 3.2.1). This is where your knowledge is tested in context, which is how many of the higher-mark exam questions are structured.
The UK government recommends that the energy in our diet should come from macronutrients in the following proportions:
| Macronutrient | Recommended % of Total Energy | Key Guidance |
|---|---|---|
| Protein | Approximately 15% | Include a variety of sources; complement LBV proteins if following a plant-based diet |
| Fat | No more than 35% (of which no more than 11% from saturated fat) | Replace saturated with unsaturated fats where possible |
| Carbohydrate | Approximately 50% (of which no more than 5% from free sugars) | Base meals on starchy carbohydrates; choose wholegrain; limit free sugars |
This means that in a typical 2,000 kcal diet for a woman or a 2,500 kcal diet for a man:
| Macronutrient | % | kcal (women, 2000 kcal) | Grams (women) | kcal (men, 2500 kcal) | Grams (men) |
|---|---|---|---|---|---|
| Protein | 15% | 300 kcal | 75 g | 375 kcal | 94 g |
| Fat | 35% (max) | 700 kcal | 78 g | 875 kcal | 97 g |
| Carbohydrate | 50% | 1,000 kcal | 267 g | 1,250 kcal | 333 g |
The energy values per gram are:
Worked example: A food label says a meal contains 30 g protein, 20 g fat, and 60 g carbohydrate. Calculate the total energy.
| Macronutrient | Grams | × kcal/g | = kcal |
|---|---|---|---|
| Protein | 30 g | × 4 | 120 kcal |
| Fat | 20 g | × 9 | 180 kcal |
| Carbohydrate | 60 g | × 3.75 | 225 kcal |
| Total | 525 kcal |
Percentage calculation:
In this case, the meal has slightly too much protein, fat is borderline, and carbohydrate is below the recommended 50%. Adding a portion of rice or bread would improve the balance.
Exam Tip: Show your working clearly when doing energy calculations. Write out the formula, show the multiplication, and state the units (kcal or kJ). Even if your final answer is wrong, you can still earn marks for correct method.
Let us analyse three different meals and assess their macronutrient balance:
| Food Item | Protein | Fat | Carbohydrate | Notes |
|---|---|---|---|---|
| 2 fried eggs | High (HBV) | High (from frying) | Low | Eggs are HBV; frying adds fat |
| 2 rashers of bacon | High (HBV) | High (saturated) | Low | Processed meat; high saturated fat |
| 1 sausage | Medium (HBV) | High (saturated) | Low | Processed meat |
| Baked beans | Medium (LBV) | Low | Medium | Good source of fibre and protein |
| 2 slices white toast | Low (LBV) | Low | High | Refined carbohydrate; low fibre |
| Butter | None | High (saturated) | None | Adds saturated fat |
Analysis: This meal is high in protein and fat (especially saturated fat) but moderate in carbohydrate. It lacks fruit and vegetables and is low in fibre.
Improvements:
| Food Item | Protein | Fat | Carbohydrate | Notes |
|---|---|---|---|---|
| Brown rice | Low (LBV) | Low | High | Complex carbohydrate; good fibre |
| Red lentils | Medium (LBV) | Low | Medium | Good protein and fibre source |
| Mixed vegetables | Low | Low | Low | Vitamins, minerals, and fibre |
| Olive oil drizzle | None | Medium (unsaturated) | None | Healthy monounsaturated fat |
Analysis: This meal demonstrates protein complementation — rice (cereal, low in lysine) combined with lentils (pulse, low in methionine) provides all essential amino acids. It is relatively low in fat and provides good carbohydrate and fibre. The fat present (olive oil) is unsaturated.
Strengths:
| Food Item | Protein | Fat | Carbohydrate | Notes |
|---|---|---|---|---|
| Beef burger | High (HBV) | High (saturated) | Low | Good protein but high fat |
| White bun | Low (LBV) | Low | High | Refined; low fibre |
| Cheese slice | Medium (HBV) | High (saturated) | Low | Adds saturated fat |
| Chips (deep fried) | Low | Very high | High | Potatoes are starchy but deep frying adds significant fat |
| Fizzy drink (330 ml) | None | None | Very high (free sugars) | Approximately 35 g of sugar — exceeds daily limit |
Analysis: This meal is very high in fat (especially saturated fat from the burger, cheese, and frying oil) and very high in free sugars (from the fizzy drink). It is low in fibre (white bun, no vegetables) and lacks fruit and vegetables.
Improvements:
The macronutrient needs of different groups vary. Here is how to adapt meals:
| Need | Reason | Practical Application |
|---|---|---|
| High energy | Rapid growth and active lifestyles | Include starchy carbohydrates at every meal |
| Adequate protein | Growth of muscles, bones, and organs | Include protein at every meal (meat, fish, eggs, beans, tofu) |
| Limit free sugars | Tooth decay is common in teenagers; obesity risk | Reduce sugary drinks, sweets, and snacks |
| Adequate fibre | Prevent constipation; long-term health | Choose wholegrain options; eat fruit and vegetables |
| Need | Reason | Practical Application |
|---|---|---|
| Extra protein (+6 g/day) | Growth of the baby, placenta, and increased blood volume | Include HBV protein sources or well-complemented LBV sources |
| Adequate fat | Baby's brain development requires essential fatty acids | Include oily fish (but limit to 2 portions per week), nuts, and seeds |
| Adequate carbohydrate | Sustained energy for mother | Base meals on starchy wholegrain carbohydrates |
| Avoid certain foods | Food safety | No raw eggs, unpasteurised cheese, liver (excess vitamin A), undercooked meat |
| Need | Reason | Practical Application |
|---|---|---|
| Adequate protein | Prevent muscle wasting (sarcopenia) | Include protein at every meal; softer options if chewing is difficult |
| Moderate fat | Maintain energy without excess weight gain | Choose unsaturated fats; limit saturated fat |
| Adequate fibre | Prevent constipation (more common with age) | Wholegrain bread, porridge, fruit, vegetables |
| Adequate calcium and vitamin D | Prevent osteoporosis | Include dairy or fortified alternatives |
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