Physical Health: Nutrition & Diet
Welcome to your revision guide for Physical Health: Nutrition. Think of your body as a high-performance sports car: what you put into your engine directly controls how fast, smooth, and long you can run. In this chapter, we will break down what makes a balanced diet, explore the seven essential nutrients, understand energy balance, and examine how our food choices impact our athletic performance and overall health.
Don't worry if this seems like a lot of information at first! We will break everything down into clear, bite-sized pieces with handy memory tricks along the way.
---1. Key Definitions: Health and a Balanced Diet
What is Health?
According to the World Health Organization (WHO), health is defined as:
"A state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity."
Within this, Physical Health refers specifically to:
• The overall condition and functioning of your body systems.
• Your nutritional status and physical fitness levels.
• The absence of illness, injury, or physical disease.
What is a Balanced Diet?
A Balanced Diet is a diet that provides the correct proportions of nutrients (carbohydrates, proteins, fats, vitamins, minerals, water, and dietary fibre) to meet the body's metabolic and energy requirements according to an individual's age, sex, body size, and activity level.
Quick Memory Tip: No single food contains all the nutrients your body needs. Balance is all about getting the right amounts of everything!
Key Takeaway: Health involves physical, mental, and social well-being. A balanced diet meets your personal energy and nutrient needs based on who you are and how active you are.
---2. The Seven Components of a Balanced Diet
Nutrients are split into two main families:
1. Macronutrients: Nutrients your body needs in large quantities for energy, growth, and repair (Carbohydrates, Proteins, and Fats).
2. Micronutrients: Nutrients your body needs in small quantities for chemical processes and protection (Vitamins and Minerals), alongside Dietary Fibre and Water.
A. Carbohydrates (Macronutrient)
Primary Function: The body’s main and most efficient source of energy for daily bodily functions and moderate-to-high intensity exercise.
Carbohydrates are broken down into glucose during digestion. Excess glucose is stored in your muscles and liver as glycogen. When you exercise, glycogen is turned back into glucose to fuel your muscles.
There are two main types of carbohydrates:
• Complex Carbohydrates (Starches): Provide slow-release energy because they take longer to digest. Examples include wholegrain bread, pasta, brown rice, potatoes, and oats. Ideal for endurance athletes who need sustained energy over long periods.
• Simple Carbohydrates (Sugars): Provide fast-release energy because they are absorbed quickly. Examples include fruit sugars (fructose), glucose energy drinks, and sweets. Ideal for a quick burst of energy during or immediately before intense exercise.
B. Proteins (Macronutrient)
Primary Function: Essential for the growth, maintenance, and repair of body tissues (especially repairing muscle fibres damaged during physical training). They also act as a secondary energy source when carbohydrate and fat stores run low.
Sources: Lean meat, poultry, fish, eggs, dairy products, soya, nuts, pulses, and legumes.
Analogy: If your body is a building site, protein represents the bricks and mortar repairing the structure after hard workouts.
C. Fats / Lipids (Macronutrient)
Primary Function: A concentrated energy source used primarily during low-intensity, long-duration aerobic exercise (like light jogging or walking). Fats also provide thermal insulation (keeping you warm), protect vital organs from shock, and carry fat-soluble vitamins (A, D, E, and K).
Fats are divided into two categories:
• Saturated Fats: Found mainly in animal products, butter, and palm oil. Eating too much saturated fat can raise blood cholesterol and increase the risk of coronary heart disease.
• Unsaturated Fats: Found in olive oil, avocados, nuts, and oily fish. These are healthier fats that support heart health.
D. Vitamins (Micronutrient)
Primary Function: Organic compounds needed in small amounts to support metabolic processes, vision, tissue health, and the immune system.
• Vitamin C: Vital for immune function, tissue repair, and producing collagen.
• Vitamin D: Crucial for helping the body absorb calcium, ensuring strong and healthy bones.
E. Minerals (Micronutrient)
Primary Function: Inorganic substances essential for physiological processes, structural development, and enzyme systems.
• Calcium: Needed for building strong bones and teeth, transmitting nerve signals, and enabling proper muscle contractions.
• Iron: An essential component of haemoglobin inside red blood cells, which binds to and transports oxygen to working muscles during exercise.
F. Dietary Fibre / Roughage
Primary Function: Fibre cannot be digested, but it plays a crucial role in regulating the digestive system. It adds bulk to stools, promotes healthy bowel movements, prevents constipation, and lowers the long-term risk of bowel diseases and bowel cancer.
Sources: Whole grains, oats, fruit skins, vegetables, and pulses.
G. Water & Hydration
Primary Function: Water accounts for the majority of body mass. It maintains blood plasma volume, regulates body temperature through sweating (thermoregulation), transports nutrients, and removes waste products.
Why Hydration Matters in Sport: During exercise, you lose water through sweat and breathing. If this fluid is not replaced, you suffer from dehydration.
• Dehydration causes a drop in blood plasma volume.
• This makes the blood thicker, meaning the heart must work harder (increasing heart rate at the same workload).
• It impairs thermoregulation (the body cannot cool itself effectively) and leads to fatigue, cramps, dizziness, and reduced physical/mental performance.
Key Takeaway: Remember the 7 components: Carbs (main fuel), Protein (repair/growth), Fats (insulation/low-intensity fuel), Vitamins (body chemistry/immunity), Minerals (bones & oxygen transport), Fibre (digestion), and Water (temperature & blood volume).
---3. Energy Balance and Caloric Requirements
The Energy Balance Equation
Energy in food is measured in calories or kilocalories (kcal). The relationship between how much energy you consume and how much you burn is known as the Energy Balance:
\(\text{Energy Intake (calories eaten)} = \text{Energy Expenditure (calories burned)}\)
• Neutral Energy Balance: \(\text{Energy Intake} = \text{Energy Expenditure}\). Body weight stays the same.
• Positive Energy Balance: \(\text{Energy Intake} > \text{Energy Expenditure}\). The excess energy is stored as body fat, leading to weight gain.
• Negative Energy Balance: \(\text{Energy Intake} < \text{Energy Expenditure}\). The body burns stored fat/glycogen for energy, leading to weight loss.
Factors Affecting Individual Nutritional Needs
Not everyone needs the exact same amount of calories or proportions of nutrients. Requirements change based on:
1. Age: Growing adolescents need more protein for tissue growth and relatively high energy compared to older adults, whose metabolism slows down.
2. Sex: Biological males generally require higher caloric intake on average than females due to a higher proportion of muscle mass and higher Basal Metabolic Rate (BMR).
3. Level & Type of Physical Activity: An endurance marathon runner requires a high proportion of complex carbohydrates to maintain glycogen stores, whereas a powerlifter requires higher protein intake for muscle repair and hypertrophy.
4. Body Size / BMR: Larger individuals with more muscle mass burn more calories even while resting.
Key Takeaway: If energy in equals energy out, your weight remains steady. Individual calorie and nutrient needs vary according to age, sex, body size, and training type.
---4. Consequences of an Unbalanced Diet
When the diet is poor or lacking balance, serious physical health problems can develop:
A. Under-Nutrition & Nutrient Deficiencies
• Iron Deficiency \(\rightarrow\) Anemia: A lack of iron reduces haemoglobin levels, impairing oxygen delivery to working muscles. This results in chronic fatigue, lethargy, and poor athletic endurance.
• Calcium & Vitamin D Deficiency \(\rightarrow\) Osteoporosis: Weakens bone mineral density, making bones fragile, brittle, and prone to fractures.
• Protein Deficiency: Leads to muscle wasting, slow recovery from training, and poor tissue repair.
• General Under-nutrition: Results in a weakened immune system, frequent illnesses, and loss of stamina.
B. Over-Nutrition & Dietary Excess
• Obesity: Carrying excessive body fat places heavy strain on joints, reduces mobility, and significantly raises the risk of Type 2 diabetes, hypertension (high blood pressure), stroke, and Coronary Heart Disease (CHD).
• High Saturated Fat & Cholesterol: Leads to atherosclerosis (the build-up of fatty plaques inside arteries), which narrows blood vessels, causes chest pain (angina), and increases the chance of heart attacks.
• High Sugar Intake: Contributes to dental caries (tooth decay), obesity, and insulin resistance leading to Type 2 diabetes.
Key Takeaway: Too little of the right nutrients causes fatigue, bone loss, and poor recovery. Too much energy or saturated fat leads to obesity, blocked arteries, and heart disease.
---5. Common Mistakes to Avoid in the Exam
Mistake 1: Confusing Macronutrients with Micronutrients
Correction: Macronutrients (Carbohydrates, Proteins, Fats) are needed in large amounts and provide bulk energy/structure. Micronutrients (Vitamins, Minerals) are needed in tiny amounts and do not directly provide energy.
Mistake 2: Thinking "All Fats Are Bad"
Correction: Fats are essential! They protect vital organs, keep us warm, absorb fat-soluble vitamins, and provide energy for low-intensity exercise. Only excess saturated fats pose health risks.
Mistake 3: Giving Vague Answers about Dehydration
Correction: Do not just write "dehydration makes you tired." Explain the physiological mechanism: dehydration lowers blood plasma volume, making the heart beat faster to maintain blood flow, while reducing the body's ability to cool down via sweating.
Mistake 4: Believing Athletes Only Need Protein
Correction: While strength athletes need protein for muscle repair, endurance athletes need large amounts of complex carbohydrates to maintain glycogen stores.
6. Quick Revision Checklist
Can you answer these key revision questions?
• Can you state the WHO definition of health from memory?
• What are the two types of carbohydrates, and when would an athlete use each?
• Why does a runner need iron in their diet?
• How does dehydration affect heart rate during exercise?
• What is the difference between a positive and negative energy balance?