Obesity is a diet-related health condition linked to an imbalance between the energy taken in from food and drink and the energy used by the body. For AQA GCSE Food Preparation and Nutrition, you need to understand energy balance, possible causes of obesity and its effects on health. This guide explains the key ideas in clear terms and shows how to apply them to food choices, lifestyle examples and exam questions. Remember that obesity is influenced by several interacting factors, so it should not be explained as simply a lack of willpower.
What is energy balance?
Energy balance is the relationship between the energy supplied by food and drink and the energy used by the body. Energy is needed for essential processes such as breathing, keeping warm and maintaining the body’s organs. It is also used for movement and physical activity.
- Energy balance: energy intake is broadly equal to energy expenditure, so body mass is likely to remain stable over time.
- Positive energy balance: energy intake is greater than energy expenditure over time. The excess energy can be stored as body fat, which may lead to weight gain and obesity.
- Negative energy balance: energy expenditure is greater than energy intake over time. This can lead to weight loss.
Energy is provided by nutrients, particularly carbohydrate, protein and fat. Fat provides more energy per gram than carbohydrate or protein, although the overall diet and portion sizes matter. Drinks and foods high in fat or free sugars can make it easier to consume more energy than the body needs, especially when eaten frequently or in large portions.
What is obesity?
Obesity is a condition in which excess body fat has accumulated and may negatively affect health. It usually develops over time when energy intake is greater than energy expenditure, but there is rarely one single cause.
Body mass index (BMI) is a calculation that compares a person’s mass with their height. It can be used as a general screening measure for body mass, but it does not directly measure body fat and does not give a complete picture of an individual’s health. For example, muscular people may have a higher BMI because muscle has mass. In an exam answer, explain what BMI can indicate rather than treating it as a perfect diagnosis.
Factors that can contribute to obesity
A strong answer recognises that obesity can have several causes. These may include:
Dietary factors
Regularly eating more energy than the body uses can cause positive energy balance. A diet high in energy-dense foods, such as foods containing a lot of fat, and frequent consumption of foods or drinks high in free sugars may contribute. Large portion sizes and frequent snacking can also increase total energy intake.
Physical activity and lifestyle
Low levels of physical activity reduce energy expenditure. A sedentary lifestyle means spending long periods sitting or being inactive. If food and drink still provide more energy than the body uses, body fat may increase over time.
Genetic and biological factors
Genes can affect characteristics such as appetite, how the body uses energy and where fat is stored. This means people can respond differently to similar diets and activity levels. Genetic factors can contribute to risk, but they do not mean that an outcome is certain.
Social, economic and psychological factors
Access to food, household income, time, cooking facilities, food marketing, stress and emotional eating can influence food choices and activity levels. These factors can interact. For example, a person’s routine, budget or living environment may make regular physical activity or preparing balanced meals more difficult.
Possible health effects of obesity
Obesity can increase the risk of a range of health problems. The risk is influenced by factors such as the amount and distribution of body fat, age, genetics and lifestyle. Possible effects include:
- type 2 diabetes, where the body does not use insulin effectively;
- high blood pressure, also called hypertension;
- cardiovascular disease, which affects the heart and blood vessels;
- greater strain on joints and reduced mobility;
- effects on mental wellbeing, which may be linked to stigma, low mood or reduced confidence.
Use careful language in examinations. Obesity can increase the risk of some conditions; it does not mean that every person with obesity will develop all of them. Health guidance can change, so use current information from the relevant official sources when checking wider health advice.
Applying the theory to food choices
Food preparation and nutrition is not about labelling individual foods as simply “good” or “bad”. A balanced approach considers the whole diet, portion size and frequency. Practical ways to support energy balance could include:
- planning meals around a variety of foods, including fruit and vegetables, starchy carbohydrates, protein sources and suitable dairy or alternatives;
- choosing lower-fat or lower-sugar options where appropriate, while considering taste, texture and nutritional value;
- checking portion sizes and avoiding unnecessary additions such as large amounts of oil, butter or sugary sauces;
- using cooking methods such as baking, grilling or steaming when they suit the dish;
- building regular physical activity into a person’s lifestyle.
In a practical evaluation, you could explain how a recipe has been adapted to reduce its energy content, for example by changing the amount of added fat or sugar and increasing vegetables. You should also consider whether the result remains appetising, safe, affordable and suitable for the intended user.
Exam-ready summary
- Define obesity as excess body fat that may negatively affect health.
- Explain energy balance using energy intake and energy expenditure.
- Link positive energy balance over time with stored body fat and possible weight gain.
- Know that dietary, lifestyle, genetic, social, economic and psychological factors may interact.
- Use examples of possible health effects, such as type 2 diabetes, hypertension and cardiovascular disease.
- Avoid blaming individuals or claiming that one food alone causes obesity.
- Use “may increase the risk” rather than presenting a possible consequence as certain.
Further specification support
For the exact AQA specification wording, check the AQA Food Preparation and Nutrition specification. Health and nutrition guidance can change, so use current information from official AQA, NHS, Food Standards Agency or GOV.UK sources when required.
Frequently asked questions
Does positive energy balance always cause obesity?
Positive energy balance over time can lead to stored body fat and weight gain. However, body mass and health are affected by many interacting factors, so an exam answer should avoid presenting obesity as having one simple cause.
Is BMI a complete measure of health?
No. BMI is a general screening measure based on mass and height. It does not directly measure body fat or account fully for muscle mass, body shape or individual circumstances.
How should I explain obesity in an exam?
Start with a clear definition, explain the energy balance, give more than one contributing factor and link obesity to possible health effects. Use cautious, accurate wording and apply the explanation to the situation in the question.