Energy use, diet, nutrition and hydration

Welcome to Energy Use, Diet, and Nutrition!

Ever wondered why some athletes eat a massive bowl of pasta before a race, or why you feel dizzy if you don't drink enough water during PE? This section is all about how we fuel our bodies and keep them running smoothly. Whether you are a marathon runner or just enjoy a walk in the park, understanding energy and nutrition is the key to performing your best!

1. Energy Use: How much fuel do you need?

Just like a car needs petrol to move, your body needs energy to function. We measure this energy in Calories (Kcal). We get these calories from the food we eat.

The Daily Averages

While everyone is different, the average guidelines for adults are:

• Average Adult Male: \(2,500 \text{ Kcal/day}\)
• Average Adult Female: \(2,000 \text{ Kcal/day}\)

Why do these numbers change?

Don't worry if you eat more or less than this! Your personal energy needs depend on four main factors. You can remember them with the mnemonic A.G.H.E. (pronounced like "age"):

1. Age: Teenagers often need more energy as they are still growing.
2. Gender: Men generally have more muscle mass, which requires more energy.
3. Height: Larger people usually need more fuel to move their larger bodies.
4. Energy Expenditure: This is just a fancy way of saying how much exercise you do. A professional footballer burns way more calories than someone sitting at a desk all day!

Quick Review: Energy is measured in Kcal. The more active you are, the more energy you need!

2. Nutrition: The Balanced Diet

There is no "magic food" that has everything you need. To stay healthy and perform well, you need a balanced diet. This means eating a variety of foods to get the right nutrients.

Why do we need a balanced diet?

• To make sure suitable energy is available for activity.
• To provide nutrients for growth and repair of tissues.
• To prevent unused energy from being stored as fat (which can lead to obesity).
• To keep the body hydrated.

The "Big Three" Nutrients (Macronutrients)

In your exam, you need to know the specific percentages for a balanced diet:

1. Carbohydrates (55–60% of your diet):
These are your body's main and preferred energy source. They provide fuel for all types of exercise, especially high-intensity activities like sprinting. Example: Pasta, potatoes, bread.

2. Fats (25–30% of your diet):
Fats provide energy too, but usually for low-intensity exercise (like a slow walk). They actually provide more energy than carbs, but the body can only use them slowly. Example: Butter, oils, avocado.

3. Protein (15–20% of your diet):
Protein is vital for the growth and repair of muscle tissue. Athletes who lift weights or do heavy training need protein to fix the tiny tears in their muscles. Example: Chicken, beans, eggs.

The "Helpers": Vitamins and Minerals

You only need these in small amounts, but they are essential for maintaining the efficient working of body systems and overall general health.
Note: You do NOT need to learn specific vitamins (like Vit C) or minerals (like Iron) for this AQA course!

Common Mistake to Avoid: Many students think fat is "bad." In PE, we learn that fat is a vital energy source for low-intensity exercise!

Key Takeaway: Carbs = Energy (Preferred), Fat = Energy (Low intensity), Protein = Growth/Repair.

3. Hydration and Water Balance

Staying hydrated isn't just about not being thirsty. It's about keeping your water balance perfect so your body can function.

What is Dehydration?

Dehydration happens when your body loses more water than it takes in (usually through sweating during exercise).

What happens if you get dehydrated?

This is a common exam question! If you don't maintain your water balance, several bad things happen:

• Blood thickening (Increased viscosity): Think of your blood turning from water into a thick milkshake. This makes it much harder for the heart to pump it around.
• Increased Heart Rate: Because the blood is thicker, the heart has to work much harder and may develop an irregular rhythm.
• Overheating: Your body can't sweat effectively to cool you down, so your body temperature rises.
• Slower Reactions: Your brain slows down, leading to poorer decision-making. (Imagine a goalkeeper missing a save because they reacted too slowly!)
• Muscle Fatigue/Cramps: Your muscles will start to ache and might painfully "lock up."

Did you know? By the time you actually feel "thirsty," your body is likely already slightly dehydrated!

Quick Review: Dehydration makes your blood viscous (thick), which makes your heart work harder and slows down your reactions.

Summary: The "Big Picture"

To be at the top of your game, you need to:
1. Balance your Kcal intake with your exercise level.
2. Eat mostly Carbohydrates for energy and Protein for repair.
3. Drink plenty of water to prevent blood thickening and fatigue.

Don't worry if these percentages seem tricky to remember at first. Just think of a plate: over half should be carbs (fuel), about a quarter should be fats, and slightly less than a quarter should be protein (building blocks)!