Unit AS 2: The Active Leisure Industry: Health, Fitness and Lifestyle

Chapter: Nutrition for Health and Exercise

Welcome to your study guide for Nutrition for Health and Exercise! Whether you are aiming for top marks or finding sports science a bit challenging, these notes break down everything you need to know for your CCEA AS 2 examination into straightforward, digestible steps. Nutrition is the fuel that powers physical activity, sustains vital bodily functions, and protects long-term health. Let's explore how food acts as fuel, building material, and medicine for the human body.

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1. Macronutrients: The Primary Energy Providers

Macronutrients are the nutrients your body needs in large daily quantities. They provide the chemical energy (measured in kilocalories, kcal, or kilojoules, kJ) required for metabolism, growth, and exercise.

A. Carbohydrates

Carbohydrates are the body's primary and preferred energy source, particularly during moderate-to-high-intensity exercise.

• Energy Yield: Approximately \(4\text{ kcal} / 17\text{ kJ}\) per gram.
• Storage and Breakdown: Dietary carbohydrates are broken down into glucose, which enters the bloodstream. Excess glucose is stored as glycogen in the skeletal muscles and the liver.
• Complex Carbohydrates (Low Glycemic Index): Provide slow, sustained energy release (e.g., wholegrain pasta, brown rice, oats). Ideal for daily meals and pre-event fuelling.
• Simple Carbohydrates / Sugars (High Glycemic Index): Rapidly digested and absorbed, causing a quick rise in blood glucose (e.g., energy gels, fruit juice). Useful for immediate energy during or straight after intense exercise.

B. Fats (Lipids)

Fats are an essential macronutrient offering dense, long-term energy storage and vital structural support.

• Energy Yield: Approximately \(9\text{ kcal} / 38\text{ kJ}\) per gram (more than double that of carbohydrates or protein!).
• Key Functions: Long-term energy storage, thermal insulation to keep the body warm, physical protection for vital organs, cell membrane structure, and production of key hormones.
• Saturated Fats: Typically solid at room temperature (e.g., butter, fatty cuts of meat). High intakes are linked to elevated blood cholesterol and cardiovascular risks.
• Unsaturated Fats: Healthier fats that are typically liquid at room temperature (e.g., olive oil, avocados, nuts). Includes essential fatty acids like Omega-3 and Omega-6, which the body cannot synthesize itself.

C. Proteins

Proteins are the structural building blocks of the body. They are made up of smaller units called amino acids.

• Energy Yield: Approximately \(4\text{ kcal} / 17\text{ kJ}\) per gram (though the body only uses protein as an energy source as a last resort, such as during extreme starvation or prolonged endurance distress).
• Essential vs Non-Essential Amino Acids: Essential amino acids must be obtained directly from the diet because the body cannot manufacture them. Non-essential amino acids can be produced internally by the body.
• Key Functions: Growth and tissue repair (especially skeletal muscle remodelling after training), synthesis of enzymes, antibodies, and vital hormones.

Examiner Pitfall Alert: Never write that protein gives the most energy per gram! Fat provides \(9\text{ kcal/g}\), whereas carbohydrates and protein both provide \(4\text{ kcal/g}\).

Section Key Takeaway: Carbohydrates fuel exercise (\(4\text{ kcal/g}\)), fats store energy and insulate (\(9\text{ kcal/g}\)), and proteins build and repair tissue (\(4\text{ kcal/g}\)).

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2. Micronutrients, Fibre, and Hydration

While macronutrients provide bulk energy, micronutrients and other dietary components ensure the body's internal engines run efficiently.

A. Vitamins

Vitamins are organic compounds required in small quantities for physiological functions:

• Fat-Soluble Vitamins (A, D, E, K): Dissolved and stored in the body's fatty tissue and liver. Vitamin D, for example, is essential for bone health and calcium absorption.
• Water-Soluble Vitamins (B-complex, C): Not stored in large amounts; regular dietary intake is required. B vitamins support energy metabolism (releasing energy from food), while Vitamin C supports immune function and tissue healing.

B. Minerals

Inorganic elements that play crucial roles in human health and athletic performance:

• Calcium: Crucial for building and maintaining strong bones and teeth, and essential for the mechanical process of muscle contraction.
• Iron: Essential for the production of haemoglobin in red blood cells, which binds and transports oxygen from the lungs to working skeletal muscles.
• Sodium and Potassium (Electrolytes): Control fluid balance across cellular membranes and enable the transmission of nerve impulses and muscle contractions.

C. Fibre (Non-Starch Polysaccharides)

Fibre is the indigestible part of plant foods. It does not provide usable calories, but it is vital for health:

• Promotes gastrointestinal motility (prevents constipation and keeps the digestive tract healthy).
• Helps regulate blood cholesterol levels and assists in steady glycemic (blood sugar) control.

D. Water and Hydration

Water constitutes roughly 60% of total body mass and is critical for survival and exercise:

• Thermoregulation: Enables cooling through the evaporation of sweat.
• Metabolic Medium: Provides the fluid environment in which cellular biochemical reactions occur.
• Transport & Lubrication: Transports nutrients, hormones, and waste products in the blood, and lubricates joints.

Section Key Takeaway: Vitamins and minerals do not provide direct calories, but without iron (oxygen transport), calcium (muscle contraction/bones), electrolytes (fluid balance/nerve impulses), and water (cooling/transport), exercise performance collapses.

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3. The Energy Balance Concept

Energy balance is the relationship between the energy you put into your body through food and drink, and the energy your body expends through daily living and exercise.

The Energy Balance Equation

\(\text{Energy Balance} = \text{Energy Intake} - \text{Energy Expenditure}\)

States of Energy Balance

• Neutral (Isocaloric) Balance: \(\text{Energy Intake} = \text{Energy Expenditure}\). Body mass remains stable.
• Positive Energy Balance: \(\text{Energy Intake} > \text{Energy Expenditure}\). Surplus energy is stored predominantly as adipose tissue (fat), leading to weight gain.
• Negative Energy Balance: \(\text{Energy Intake} < \text{Energy Expenditure}\). The body mobilises stored glycogen and adipose tissue to meet energy demands, leading to weight loss.

Components of Total Daily Energy Expenditure (TDEE)

Where does the energy you burn each day actually go? It is divided into three components:

1. Basal Metabolic Rate (BMR): Accounts for 60–75% of TDEE. This is the minimum energy required to keep vital organs functioning (heart beating, lungs breathing, brain functioning) while completely at rest.
2. Physical Activity Level (PAL): Accounts for 15–30% of TDEE. This is the energy used during all voluntary movement, including daily walking, chores, and structured sports training.
3. Thermic Effect of Food (TEF): Accounts for approximately 10% of TDEE. This represents the metabolic energy required to digest, absorb, and process the nutrients in your meals.

Memory Tip: Remember B-P-T for the components of TDEE: BMR (the biggest chunk, ~70%), PAL (movement), and TEF (digestion, ~10%).

Section Key Takeaway: Weight changes depend on energy balance. BMR is the largest component of daily expenditure (\(60\text{–}75\%\)), followed by physical activity (\(15\text{–}30\%\)) and the thermic effect of food (\(\sim 10\%\)).

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4. Nutrition for Exercise Performance and Recovery

Athletes use targeted nutritional strategies before, during, and after exercise to maximise performance, maintain hydration, and speed up recovery.

A. Pre-Exercise Nutrition (Fuelling Up)

• Meal Timing: Consume a meal rich in complex carbohydrates (low-to-medium GI) approximately 2.5 to 4 hours before exercise. This maximises liver and muscle glycogen stores without causing stomach discomfort.
• Pre-Hydration: Drink approximately \(5\text{ to }7\text{ ml/kg}\) of body mass of fluid roughly 2 to 4 hours prior to training or competition to ensure proper hydration before the start.

B. Nutrition During Exercise (Sustaining Output)

• For exercise lasting longer than 60 minutes, muscle glycogen stores become depleted.
• Athletes should consume 30 to 60 grams of simple carbohydrates per hour (e.g., energy gels, sports drinks) to maintain blood glucose levels and delay fatigue.
• Consuming fluid with electrolytes (sodium) prevents dehydration and maintains electrolyte balance.

C. Post-Exercise Recovery (The "Window of Opportunity")

Recovery nutrition focuses on three goals: Refuel, Rebuild, and Rehydrate.

• The "Window of Opportunity" (30–60 Minutes): Immediately after exercise, muscle cells are primed to absorb glucose and amino acids rapidly.
• Carbohydrate-to-Protein Ratio: Consuming a meal or recovery drink with a 3:1 or 4:1 ratio of carbohydrate to protein within the first 30–60 minutes accelerates glycogen resynthesis and triggers muscle protein synthesis for tissue repair.
• Rehydration Strategy: Athletes should consume fluid containing sodium equal to 1.25 to 1.5 times the total fluid mass lost (measured by weighing before and after exercise) to fully restore hydration status.

Examiner Pitfall Alert: When discussing rehydration, do not just write "drink plain water." Marks are awarded for specifying the replacement of fluid and electrolytes (specifically sodium) at a volume of \(1.25\text{–}1.5\) times the fluid lost.

Section Key Takeaway: Fuel with complex carbs 2.5–4 hours pre-event; top up with \(30\text{–}60\text{ g/hour}\) simple carbs for sessions >60 mins; and recover within 30–60 mins using a 3:1/4:1 carb-to-protein ratio and sodium-containing fluids.

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Poor dietary habits and chronic positive energy balance are major contributing factors to lifestyle-related chronic diseases in the active leisure and healthcare sectors.

Diet-Related Health Conditions

• Obesity: Chronic positive energy balance leads to excessive accumulation of adipose tissue, which places significant stress on the musculoskeletal and cardiovascular systems.
• Type 2 Diabetes: Often linked to excess body weight and physical inactivity. The body's cells become resistant to insulin, leading to chronically elevated blood glucose levels.
• Atherosclerosis: Diets high in saturated and trans fats lead to the build-up of fatty plaques inside arterial walls, narrowing blood vessels and restricting blood flow.
• Hypertension: High blood pressure, often exacerbated by excessive dietary sodium intake, obesity, and poor arterial elasticity.
• Cardiovascular Disease (CVD): An umbrella term covering heart and circulatory conditions (including heart attacks and strokes), heavily influenced by poor diet, atherosclerosis, and hypertension.

Public Health and Dietary Guidelines

Public health strategies and national dietary reference standards aim to educate populations, reduce saturated fat and sugar consumption, and encourage physical activity to decrease the prevalence of these chronic lifestyle conditions.

Section Key Takeaway: Chronic excess intake of saturated fats and calories directly increases risks for obesity, Type 2 diabetes, atherosclerosis, hypertension, and cardiovascular disease.

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6. Quick Revision & Exam Checklist

Use this checklist to test your knowledge before sitting the AS 2 exam:

• Can you state the energy values per gram for carbohydrates (\(4\text{ kcal} / 17\text{ kJ}\)), fats (\(9\text{ kcal} / 38\text{ kJ}\)), and proteins (\(4\text{ kcal} / 17\text{ kJ}\))?
• Can you explain the roles of Calcium (bones and muscle contractions) and Iron (haemoglobin and oxygen transport)?
• Can you outline the three components of TDEE (BMR: 60–75%, PAL: 15–30%, TEF: ~10%)?
• Do you know the pre-exercise meal timing (2.5–4 hours) and post-exercise recovery ratio (3:1 or 4:1 carb-to-protein within 30–60 minutes)?
• Can you explain how poor diet leads to chronic conditions such as atherosclerosis, hypertension, and Type 2 diabetes?