Obesity and Type 2 Diabetes

This lesson covers the diet-related health conditions of obesity and type 2 diabetes, as required by AQA GCSE Food Preparation and Nutrition specification 8585, section 3.2.3. You must understand the causes, health risks, and prevention strategies for both conditions, and explain the links between diet, energy balance, and these diseases.

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Obesity

What Is Obesity?

Obesity is a condition in which a person has an abnormally high and unhealthy amount of body fat. It is caused by a sustained positive energy balance — consuming more energy (calories) from food and drink than the body uses through BMR, physical activity, and the thermic effect of food. The excess energy is stored as adipose tissue (body fat).

Obesity is measured using Body Mass Index (BMI):

BMI Range	Classification
Below 18.5	Underweight
18.5–24.9	Healthy weight
25.0–29.9	Overweight
30.0 and above	Obese
40.0 and above	Morbidly obese

BMI = weight (kg) ÷ height² (m²)

For example, a person weighing 90 kg who is 1.75 m tall: BMI = 90 ÷ (1.75 × 1.75) = 90 ÷ 3.0625 = 29.4 (overweight)

Exam Tip: BMI is a useful screening tool but has limitations. It does not distinguish between fat and muscle (a muscular athlete may have a high BMI but low body fat). Waist circumference is also used as a measure of health risk — excess fat around the waist (abdominal obesity) is particularly dangerous.

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Causes of Obesity

Cause	Explanation
Excessive energy intake	Eating too many high-energy, high-fat, high-sugar foods (e.g. fast food, sugary drinks, snacks, large portions)
Insufficient physical activity	Sedentary lifestyle — too much sitting, screen time, driving instead of walking
Portion sizes	Restaurant and shop portions have increased significantly over the decades
Availability of cheap, energy-dense food	Fast food, processed meals, and sugary drinks are widely available and heavily marketed
Emotional and psychological factors	Comfort eating, stress, depression, boredom can all lead to overeating
Genetics	Some people have a genetic predisposition to store fat more easily, but genetics alone rarely cause obesity without environmental factors
Socioeconomic factors	People on lower incomes may have less access to fresh, healthy food and rely on cheaper, processed alternatives
Lack of nutritional knowledge	Some people do not understand how to plan a balanced diet or read food labels

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Health Risks of Obesity

Obesity significantly increases the risk of many serious health conditions:

Health Risk	How Obesity Contributes
Type 2 diabetes	Excess body fat (especially around the abdomen) causes cells to become resistant to insulin, leading to high blood sugar
Cardiovascular disease (CVD)	Obesity increases blood pressure, cholesterol, and strain on the heart
Stroke	High blood pressure and blocked arteries increase stroke risk
Certain cancers	Including bowel, breast, kidney, and liver cancer
Joint problems	Excess weight puts strain on joints (especially knees and hips), leading to osteoarthritis
Sleep apnoea	Fat deposits around the airway can cause breathing difficulties during sleep
Mental health	Depression, low self-esteem, and social isolation
Reduced life expectancy	Obesity reduces average lifespan by several years
Liver disease	Non-alcoholic fatty liver disease (NAFLD) caused by fat accumulation in the liver

graph TD
    A["Obesity<br/>(BMI ≥ 30)"] --> B["Type 2 Diabetes"]
    A --> C["Cardiovascular Disease"]
    A --> D["Stroke"]
    A --> E["Certain Cancers"]
    A --> F["Joint Problems"]
    A --> G["Sleep Apnoea"]
    A --> H["Mental Health Issues"]
    A --> I["Reduced Life Expectancy"]

    J["Causes"] --> A
    J1["Excess energy intake"] --> J
    J2["Low physical activity"] --> J
    J3["Large portion sizes"] --> J
    J4["Cheap energy-dense food"] --> J

    style A fill:#e74c3c,color:#fff
    style J fill:#f39c12,color:#fff
    style B fill:#8e44ad,color:#fff
    style C fill:#8e44ad,color:#fff

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Preventing and Managing Obesity

Strategy	Details
Reduce energy intake	Choose smaller portions, reduce high-fat and high-sugar foods, follow the Eatwell Guide
Increase physical activity	At least 150 minutes of moderate exercise per week (e.g. brisk walking, cycling, swimming)
Eat more fruit, vegetables, and fibre	These are filling but lower in energy, helping to control appetite
Choose wholegrain carbohydrates	Wholegrain foods release energy more slowly, helping to maintain blood sugar and reduce hunger
Limit sugary drinks	Sugary drinks are a major source of "hidden" calories with no nutritional benefit
Cook at home	Home-cooked meals tend to be lower in fat, sugar, and salt than takeaways and ready meals
Read food labels	Use traffic light labelling and nutrition information to make healthier choices
Eat regular meals	Skipping meals often leads to overeating later

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Type 2 Diabetes

What Is Type 2 Diabetes?

Type 2 diabetes is a condition in which the body either does not produce enough insulin or the body's cells do not respond properly to insulin (insulin resistance). Insulin is a hormone produced by the pancreas that allows glucose to enter cells from the blood to be used for energy.

In type 2 diabetes:

1. The body's cells become resistant to insulin — they do not respond to it properly.
2. The pancreas tries to compensate by producing more insulin, but eventually cannot keep up.
3. Glucose builds up in the blood (hyperglycaemia — high blood sugar) instead of entering cells.
4. Over time, high blood sugar damages blood vessels, nerves, and organs.