Lifestyle and disease (AQA GCSE Biology Combined Science): Revision Notes
Lifestyle and disease
Lifestyle factors like diet and exercise can significantly affect your risk of getting certain diseases. Understanding these links helps us make better choices for our health and take control of preventable health risks.
The relationship between lifestyle and disease is complex, involving both factors we can control (like diet and exercise) and factors we cannot (like our genetic inheritance).
Exercise and disease
Obesity means being very overweight. It's a major lifestyle risk factor that increases your chances of getting diseases.
How obesity affects health
Obesity increases the risk of several serious health conditions:
- Type 2 diabetes - when your body can't control blood sugar properly
- Cardiovascular disease - problems with your heart and blood vessels
These are not minor health issues - Type 2 diabetes and cardiovascular disease are among the leading causes of death worldwide. The good news is that obesity, being a lifestyle factor, can often be prevented or managed through diet and exercise.
Benefits of regular exercise
Exercise helps protect your health in two main ways:
- Better weight control - helps you maintain a healthy body weight
- Better overall health - strengthens your heart and improves fitness
People who exercise regularly are less likely to develop these diseases because they can better control their body mass.
Regular exercise doesn't just help with weight - it also improves insulin sensitivity, strengthens the heart muscle, and helps maintain healthy blood pressure levels.
Risk factors vs inherited factors
Lifestyle risk factors
These are things we can control, like:
- Diet choices
- Amount of exercise
- Smoking habits
Inherited factors
These come from our genes and we cannot change them:
- Some people inherit alleles (versions of genes) that affect their cholesterol levels
- They might have higher cholesterol even if they eat the same diet as someone else
- This shows that genes can affect health too
Understanding the Gene-Lifestyle Balance
While we cannot change our genetic inheritance, lifestyle choices still matter enormously. Even people with genetic predispositions can often reduce their disease risk through healthy lifestyle choices, though they may need to work harder than others to achieve the same results.
Why this matters for studies
When scientists study lifestyle factors, they must compare people with similar inherited factors. This makes sure the results are valid (reliable and accurate).
Study Design Example: Testing Exercise Benefits
To test if exercise prevents heart disease:
- Compare two groups with similar genetic backgrounds
- One group exercises regularly, one doesn't
- Measure heart disease rates in both groups
- Any difference can be attributed to exercise, not genetics
Understanding cancer
Cancer happens when cells change and start growing and dividing in an uncontrolled way.
Types of tumours
There are two main types of tumours with very different characteristics:
Benign tumours:
- Made of abnormal cells
- Stay in one place, usually inside a membrane
- Don't spread to other parts of the body
- Not cancerous
Malignant tumours:
- These are actual cancers
- Invade nearby tissues
- Spread through the blood to other body parts
- Form secondary tumours in different locations
The key difference is that malignant tumours have the dangerous ability to spread (metastasize) throughout the body, while benign tumours remain localised.
What causes cancer
Scientists have identified several proven causes of cancer:
- Carcinogens - poisonous substances that damage cells
- Ionising radiation - harmful radiation that changes cells
Proven vs Suspected Causes
It's important to distinguish between scientifically proven causes of cancer (like certain chemicals and radiation) and suspected or possible causes that are still being researched. Only factors with strong scientific evidence should guide major health decisions.
How scientists study lifestyle and disease
Many diseases are caused by different factors working together. Scientists need to show:
- That a risk factor actually causes the disease
- How this process works in the body
Control groups
When testing if lifestyle changes help prevent disease, scientists use:
- One group that gets advice (test group)
- One group that gets no advice (control group)
- This helps prove whether the lifestyle change actually works
Why Control Groups Matter
Without control groups, scientists cannot tell whether health improvements are due to the lifestyle intervention or other factors like natural recovery, placebo effects, or seasonal variations in health.
The more people involved in a study, the more reliable the results become.
Study Design: Testing Dietary Advice
Step 1: Recruit 1000 people with high cholesterol Step 2: Randomly divide into two groups of 500 each Step 3: Give dietary advice to one group, standard care to the other Step 4: Monitor cholesterol levels for 12 months Step 5: Compare results between groups to see if dietary advice worked
Key Points to Remember:
- Obesity increases risk of Type 2 diabetes and heart disease
- Regular exercise helps control weight and improves health
- Inherited factors can't be changed but affect disease risk
- Benign tumours stay in one place, malignant tumours spread around the body
- Scientists need control groups to prove lifestyle factors cause or prevent disease
- Both genetic and lifestyle factors work together to determine disease risk