In simple terms
A friendly intro before the formal notes — no formulas yet.
Your Body's Fuel Mix
Just as a car needs the right type and amount of fuel to run efficiently, your body requires a balanced mix of nutrients to function, grow, and repair. This balance is essential for maintaining daily health and achieving peak athletic performance.
Think of your body as a high-performance racing car. You wouldn't put cheap, low-grade petrol in a Formula 1 car and expect it to win a race. Similarly, your body needs premium fuel—a balanced diet rich in varied nutrients—to perform at its best, recover from exercise, and stay healthy long-term. Relying on 'junk food' is like using the wrong fuel; the engine will eventually splutter and break down.
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First, identify the six essential nutrient categories: carbohydrates, proteins, fats, vitamins, minerals, and water. Understand their distinct roles in providing energy, building tissues, and regulating bodily processes.
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Next, analyse the concept of energy balance by comparing energy intake (kilocalories from food) with energy expenditure (from metabolism, daily activities, and exercise). This relationship dictates whether body mass is maintained, gained, or lost.
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Then, learn to evaluate dietary intake using common assessment methods like a food diary, 24-hour recall, or a food frequency questionnaire. Be prepared to discuss the strengths and limitations of each method.
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Finally, connect dietary patterns to long-term health. Explain how imbalances, such as excessive intake of saturated fats or sugars, can increase the risk of developing chronic diseases like obesity and type 2 diabetes.
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Key formulas
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Full topic notes
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Components of a Balanced Diet
A balanced diet is not a 'one-size-fits-all' prescription. It involves consuming a variety of foods in the right proportions to supply the body with adequate energy and nutrients for its needs. These needs are highly individual, influenced by factors like age, gender, body size, and, crucially for this course, physical activity level. The main components are macronutrients, micronutrients, water, and fibre.
Macronutrients: Carbohydrates, proteins, and fats, required in large amounts for energy and structure.
Micronutrients: Vitamins and minerals, required in small amounts for metabolic processes.
Water: Essential for hydration, temperature regulation, and transporting nutrients.
Fibre: A type of carbohydrate important for digestive health.
Macronutrient Roles and Energy Yield
Each macronutrient provides a specific amount of energy, typically measured in kilocalories (kcal) or kilojoules (kJ). Understanding their energy yield is fundamental to calculating energy intake and managing energy balance.
Energy per gram:
- Carbohydrate = 4 kcal (17 kJ)
- Protein = 4 kcal (17 kJ)
- Fat = 9 kcal (37 kJ)
General dietary recommendations for a sedentary adult suggest a macronutrient split of approximately 45-65% carbohydrates, 20-35% fats, and 10-35% protein. However, an endurance athlete's needs may shift towards higher carbohydrate intake (e.g., 60-70%) to fuel prolonged activity.
Dietary Assessment Methods
To understand the relationship between diet and health, we must first be able to measure what people eat. This is challenging, as it often relies on self-reporting, which can be prone to error. Several methods are used, each with distinct advantages and disadvantages.
24-hour Dietary Recall: A structured interview where the individual recounts everything they ate and drank in the last 24 hours. Quick and low respondent burden, but relies on memory and may not be a typical day.
Food Frequency Questionnaire (FFQ): A questionnaire asking how often an individual consumes specific food items from a list over a set period (e.g., last month). Good for assessing long-term intake patterns but lacks detail on portion sizes and specific food preparation.
Food Diary/Record: The individual records all food and beverages consumed over a specific period (e.g., 3-7 days) at the time of consumption. Provides detailed, real-time data but is burdensome and can lead to changes in eating behaviour (reactivity).
For evaluation questions on dietary assessment, always provide both a strength and a limitation for each method discussed. For example, a food diary is 'more accurate as it is recorded in real-time' (strength), but 'the act of recording can cause the individual to alter their normal eating habits' (limitation). Using comparative language like 'more' or 'less' is also good practice.
Worked examples
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A cyclist consumes 4000 kcal per day to fuel their training. Their diet consists of 60% carbohydrate, 25% fat, and 15% protein. Calculate the mass (in grams) of each macronutrient they consume daily.
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Calculate kcal from each macronutrient:
A male office worker is 1.78 m tall and has a mass of 85 kg. Calculate his Body Mass Index (BMI) and state the WHO classification for his result. Outline one major limitation of using BMI to assess the health of an athlete.
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State the formula for BMI:
How it all connects
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Glossary
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Revision flashcards
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What is a balanced diet?
A diet that provides all the essential nutrients (macronutrients, micronutrients), water, and fibre in the correct proportions to maintain health and well-being. Proportions vary based on age, sex, and activity level.
Key takeaways
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Macronutrients: Carbohydrates, proteins, and fats, required in large amounts for energy and structure.
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Micronutrients: Vitamins and minerals, required in small amounts for metabolic processes.
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Water: Essential for hydration, temperature regulation, and transporting nutrients.
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Fibre: A type of carbohydrate important for digestive health.
Practice — then mark it
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Test Your Knowledge on Nutrition and Health
Test Your Knowledge on Nutrition and Health
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