Chapter 7 of 8

All 8 chapters
  1. 1Kinds of disease, readunderstood
  2. 2How diseases spread, readunderstood
  3. 3The body's defences, readunderstood
  4. 4Vaccination, readunderstood
  5. 5Antibiotics and medicines, readunderstood
  6. 6Malaria, HIV and tuberculosis, readunderstood
  7. 7Lifestyle and disease, readunderstood
  8. 8Sexual health, readunderstood

S4.4.7 Chapter 7

Lifestyle and disease

Can the way I live make me ill, even if I never catch a germ?

Your guess

Pick one before you read on. It is fine to be wrong.

Your guess

  • You picked A. Read on. At the end, the chapter comes back to your guess.

  • You picked B. Read on. At the end, the chapter comes back to your guess.

  • You picked C. Read on. At the end, the chapter comes back to your guess.

By the end you can

  • Explain links between diet, smoking, alcohol and heart disease
  • Calculate body mass index and explain its limits

In the first chapter, you met non-communicable diseases. No pathogen causes them and nobody can catch them. Many have more than one cause. Some causes are in your genes, and some are in how you live. This chapter follows one disease, heart disease, and then a way to measure body size.

A risk factor is something that raises the chance of getting a disease. It does not decide it. Some people with risk factors never become ill, and some people with none do. The more risk factors a person has, the higher the chance. Some risk factors, such as age and the genes you inherit, cannot be changed. Others can.

The heart is a muscle, and it needs oxygen like any other. It gets blood through arteries on its own surface. In heart disease, these arteries narrow. A fatty deposit builds up inside the wall of an artery, as the picture shows, and the space for blood gets smaller.

Draw it first

An artery narrows and blocks

  1. Three pictures of a long section of an artery, drawn on top of each other. First the space for blood is the same width all along. Then a dotted fatty deposit grows on the wall and makes it narrower. Last the deposits meet and block it. A hatched wall runs along the top and another along the bottom, and an arrow points along the space. The labels are artery wall, blood flow and fatty deposit.bloodflowarterywall

    1 A healthy artery has smooth walls. Blood flows freely along it.

  2. Three pictures of a long section of an artery, drawn on top of each other. First the space for blood is the same width all along. Then a dotted fatty deposit grows on the wall and makes it narrower. Last the deposits meet and block it. A hatched wall runs along the top and another along the bottom, and an arrow points along the space. The labels are artery wall, blood flow and fatty deposit.bloodflowarterywallfattydeposit

    2 A fatty deposit builds up on the wall. The space is narrower, so less blood passes. The heart muscle may get too little oxygen when it works hard.

  3. Three pictures of a long section of an artery, drawn on top of each other. First the space for blood is the same width all along. Then a dotted fatty deposit grows on the wall and makes it narrower. Last the deposits meet and block it. A hatched wall runs along the top and another along the bottom, and an arrow points along the space. The labels are artery wall, blood flow and fatty deposit.bloodflowarterywallfattydeposit

    3 In time the deposit can block the artery. The part of the heart muscle that the artery feeds then gets no blood. The muscle there can be damaged. This is a heart attack.

Fatty deposits can also build up in arteries that go to the brain. A blockage there can cause a stroke. The same habits that raise the risk of heart disease also raise the risk of stroke.

Which habits raise the risk? A diet with a lot of saturated fat does. Saturated fat is found in fatty meat, butter and some oils. It helps the deposits to form. A lot of salt in the diet raises blood pressure, which is the pressure of the blood on the artery walls. High blood pressure strains the heart and damages the arteries.

Smoking harms the arteries. Chemicals in the smoke damage their walls, which helps deposits to form. Smoking also raises the heart rate and the blood pressure, and it lowers the oxygen that the blood can carry. Smoke is harmful to people nearby, too. A person who smokes and wants to stop can ask a health worker for help. The risk falls after stopping.

Drinking a lot of alcohol over many years raises the blood pressure and can damage the heart muscle and the liver. Alcohol also adds energy to the diet and can lead to weight gain. Too little exercise lets the heart muscle weaken, and exercise helps to control weight and blood pressure.

A table with the columns Habit, Harm. fatty food, deposits. salty food, blood pressure. smoking, artery damage. alcohol, blood pressure. no exercise, weak heart.HabitHarmfatty fooddepositssalty foodblood pressuresmokingartery damagealcoholblood pressureno exerciseweak heart
Habits that raise the risk of heart disease and the harm each does. Fatty food means food with a lot of saturated fat. Deposits are fatty deposits.

A balanced diet with little saturated fat and salt, no smoking, little alcohol and regular exercise all lower the risk. None of these guarantees good health. They change the odds.

Try it

Find the fat in food

You need: plain paper, a pencil, a drop of cooking oil, a little margarine, a slice of bread, a slice of apple.

Be safe: Do not taste the food you rubbed on the paper. Wash your hands afterwards. Do not use nuts, because some people are allergic to them.

  1. Write the name of each food on the paper, in a row, with space beside it.
  2. Rub each food once on the paper beside its name. Do not press hard.
  3. Leave the paper in a warm, dry place until all the marks have dried. This takes some time.
  4. Hold the paper up to the light. Look for a spot that stays clear, so that you can see through it.

What you will see: The oil and the margarine leave a clear spot, which is fat. The bread and the apple leave none once they have dried. The test finds fat. It does not say whether the fat is saturated. The body needs some fat, so the point is how much and which kind.

If you cannot try it, this is what happens.
A table with the columns Food, Spot. cooking oil, clear. margarine, clear. bread, none. apple, none.FoodSpotcooking oilclearmargarineclearbreadnoneapplenone

Now to measure body size. Body mass index, or BMI, compares a person's mass with their height. The formula is mass in kilograms divided by the square of height in metres. A square means a number multiplied by itself.

See it three ways

As a picture

A table with the columns BMI, Band. under 18.5, underweight. 18.5 to 24.9, healthy weight. 25 to 29.9, overweight. 30 or more, obese.BMIBandunder 18.5underweight18.5 to 24.9healthy weight25 to 29.9overweight30 or moreobese

In words

BMI is mass divided by height squared. The table gives the usual bands for adults. Health workers use it as a quick check on the body size of a group or a person. It is a screening number, not a diagnosis.

In symbols

BMI = mass in kg ÷ height in m ÷ height in m. For 60 kg and 1.60 m, BMI = 60 ÷ 1.60 ÷ 1.60 = 23.4.

The bands are for adults. For children and teenagers, health workers use charts for age and sex instead, because their bodies are still growing. In some places the cut offs differ a little for some groups of people.

Worked example

Ana has a mass of 60 kg and a height of 1.60 m. Work out her BMI, and say which adult band it is in.

  1. Height squared: 1.60 × 1.60 = 2.56.
  2. BMI = mass ÷ height squared = 60 ÷ 2.56 = 23.4, to one decimal place.
  3. 23.4 is from 18.5 up to 25, so the band is healthy weight.

Answer: 23.4, in the healthy weight band

Worked example

Kofi has a mass of 95 kg and a height of 1.80 m. Work out his BMI, and say which adult band it is in.

  1. Height squared: 1.80 × 1.80 = 3.24.
  2. BMI = mass ÷ height squared = 95 ÷ 3.24 = 29.3, to one decimal place.
  3. 29.3 is from 25 up to 30, so the band is overweight.

Answer: 29.3, in the overweight band

A table with the columns Mass, Height, BMI. 60 kg, 1.60 m, 23.4. 95 kg, 1.80 m, 29.3.MassHeightBMI60 kg1.60 m23.495 kg1.80 m29.3
The two examples above, in one table. BMI is rounded to one decimal place.

BMI has limits. Muscle weighs more than fat of the same size. A person with a lot of muscle can have a high BMI and little fat. BMI does not show where fat is carried, and fat around the waist raises risk the most. A waist measurement adds that information.

BMI is not used on its own for children and teenagers, who need age charts. Nor is it used in pregnancy, when the mass rises for a good reason. In older adults, muscle loss can hide extra fat. And BMI says nothing about diet, fitness or blood pressure. A health worker looks at all of these.

A wrong idea many people have

BMI tells you exactly whether a person is healthy.

Why it feels right: It gives one clear number and a named band, so it looks like a final answer.

The test that breaks it: Take two adults with the same BMI. One is a runner with strong muscles. The other has little muscle and carries fat round the waist. Their BMI is the same, but their health may be very different.

What is true: BMI is a quick check, not a diagnosis. It is one number that a health worker uses with others.

Key words

heart disease
a disease in which arteries that feed the heart muscle narrow, so less blood reaches it.
risk factor
something that raises the chance of getting a disease.
fatty deposit
fatty material that builds up in the wall of an artery and narrows it.
saturated fat
a kind of fat found in fatty meat, butter and some oils. A lot of it raises the risk of heart disease.
blood pressure
the pressure of the blood on the walls of the arteries.
body mass index
mass in kilograms divided by the square of height in metres.

Back to your guess

The answer is C: Yes. Diet, smoking, alcohol and too little exercise can raise the risk of diseases such as heart disease.

Many non-communicable diseases have several causes. Genes and age matter, and so do what we eat and drink, whether we smoke and how active we are. These habits raise or lower the risk. They do not decide it.

Check yourself

Try each one before you look. A wrong answer tells you where to go next.

  1. What narrows an artery in heart disease?

    Tap your answer.

    1. Not this one. White blood cells fight pathogens. They do not block arteries in heart disease. Try another.

    2. Yes, that is right. Fatty material builds up inside the wall of an artery. The space for blood gets smaller, and less blood reaches the heart muscle.

    3. Not this one. Mucus is made in the airways to trap pathogens. It does not enter the arteries. Try another.

    4. Not this one. Heart disease is non-communicable. It is not caused by a pathogen. Go to S4.4.1. Try another.

    See the answer

    A fatty deposit that builds up in the wall.

    Fatty material builds up inside the wall of an artery. The space for blood gets smaller, and less blood reaches the heart muscle.

    • If you chose A: White blood cells fight pathogens. They do not block arteries in heart disease.
    • If you chose C: Mucus is made in the airways to trap pathogens. It does not enter the arteries.
    • If you chose D: Heart disease is non-communicable. It is not caused by a pathogen. Go to S4.4.1.

  2. Look at the picture of an artery. What is the likely result for the heart muscle that this artery feeds?

    A long section of an artery, seen from the side. A hatched wall runs along the top and another along the bottom. The space between them is where blood flows. Dotted fatty deposits grow from the top and the bottom until they meet in the middle, so the space is blocked. An arrow points along it and stops short of the block. The labels are artery wall, fatty deposit and blood flow.bloodflowarterywallfattydeposit
    Tap your answer.

    1. Not this one. A blocked artery lets no blood through, so the muscle gets less blood, not more. Try another.

    2. Not this one. Blood cannot pass a block. The muscle beyond it can be damaged. Try another.

    3. Yes, that is right. The deposits block the artery, so the part of the heart muscle that it feeds gets no blood and no oxygen. That is a heart attack.

    See the answer

    It gets too little blood and oxygen, and may be damaged.

    The deposits block the artery, so the part of the heart muscle that it feeds gets no blood and no oxygen. That is a heart attack.

    • If you chose A: A blocked artery lets no blood through, so the muscle gets less blood, not more.
    • If you chose B: Blood cannot pass a block. The muscle beyond it can be damaged.

  3. Why does smoking raise the risk of heart disease?

    Tap your answer.

    1. Not this one. Smoke also harms the arteries and raises blood pressure. It harms the heart as well. Go to S3.3.8. Try another.

    2. Yes, that is right. Chemicals in smoke damage the wall of an artery, and nicotine raises blood pressure. Both raise the risk of heart disease.

    3. Not this one. Smoke does not turn into fat. It damages the artery wall, which helps deposits to form. Try another.

    See the answer

    Chemicals in smoke damage artery walls, and smoking raises blood pressure.

    Chemicals in smoke damage the wall of an artery, and nicotine raises blood pressure. Both raise the risk of heart disease.

    • If you chose A: Smoke also harms the arteries and raises blood pressure. It harms the heart as well. Go to S3.3.8.
    • If you chose C: Smoke does not turn into fat. It damages the artery wall, which helps deposits to form.

  4. Which of these does not raise the risk of heart disease?

    Tap your answer.

    1. Not this one. A lot of salt raises blood pressure, which raises the risk. Try another.

    2. Not this one. Saturated fat helps fatty deposits to form, which raises the risk. Try another.

    3. Not this one. It raises blood pressure and can damage the heart, so it raises the risk. Try another.

    4. Yes, that is right. Exercise strengthens the heart, helps to control weight and blood pressure, and so lowers the risk.

    See the answer

    Regular exercise.

    Exercise strengthens the heart, helps to control weight and blood pressure, and so lowers the risk.

    • If you chose A: A lot of salt raises blood pressure, which raises the risk.
    • If you chose B: Saturated fat helps fatty deposits to form, which raises the risk.
    • If you chose C: It raises blood pressure and can damage the heart, so it raises the risk.

  5. What does it mean to call something a risk factor?

    Tap your answer.

    1. Not this one. A risk factor raises the chance. Some people with it never become ill. Try another.

    2. Yes, that is right. Smoking and too little exercise are risk factors for heart disease. They raise the chance. They do not decide whether a person becomes ill.

    3. Not this one. A pathogen is a germ. A risk factor can be anything that raises the chance, such as a habit. Try another.

    See the answer

    It raises the chance of getting the disease.

    Smoking and too little exercise are risk factors for heart disease. They raise the chance. They do not decide whether a person becomes ill.

    • If you chose A: A risk factor raises the chance. Some people with it never become ill.
    • If you chose C: A pathogen is a germ. A risk factor can be anything that raises the chance, such as a habit.

  6. Why can BMI mislead for a person with a lot of muscle?

    Tap your answer.

    1. Not this one. It is the other way round. Muscle weighs more than fat for the same size. Try another.

    2. Not this one. BMI uses both mass and height. Try another.

    3. Yes, that is right. BMI uses mass, and it cannot tell muscle from fat. A very muscular person can have a high BMI and little fat.

    4. Not this one. BMI is for any adult. It is only limited because it cannot tell muscle from fat. Try another.

    See the answer

    Muscle weighs more than fat, so mass can be high without much fat.

    BMI uses mass, and it cannot tell muscle from fat. A very muscular person can have a high BMI and little fat.

    • If you chose A: It is the other way round. Muscle weighs more than fat for the same size.
    • If you chose B: BMI uses both mass and height.
    • If you chose D: BMI is for any adult. It is only limited because it cannot tell muscle from fat.

  7. Which group should not be judged by the adult BMI bands alone?

    Tap your answer.

    1. Not this one. The adult bands are the same for men and women. Try another.

    2. Yes, that is right. Their bodies are still growing, so health workers compare them with charts for their age and sex.

    3. Not this one. BMI already allows for height. The adult bands are the same for short and tall adults. Try another.

    See the answer

    Children and teenagers, who need charts for age and sex.

    Their bodies are still growing, so health workers compare them with charts for their age and sex.

    • If you chose A: The adult bands are the same for men and women.
    • If you chose C: BMI already allows for height. The adult bands are the same for short and tall adults.

  8. From an earlier chapter

    Heart disease and influenza are both diseases. What is the main difference?

    Tap your answer.

    1. Yes, that is right. Influenza is communicable. Heart disease has causes such as fatty deposits and habits, and nobody can catch it.

    2. Not this one. It is the other way round. A virus causes influenza, and it spreads between people. Go to S4.4.1. Try another.

    3. Not this one. Influenza is caused by a virus, and heart disease is not caused by a pathogen. Go to S4.4.1. Try another.

    See the answer

    Influenza is caused by a pathogen and can pass between people. Heart disease is not and cannot.

    Influenza is communicable. Heart disease has causes such as fatty deposits and habits, and nobody can catch it.

    • If you chose B: It is the other way round. A virus causes influenza, and it spreads between people. Go to S4.4.1.
    • If you chose C: Influenza is caused by a virus, and heart disease is not caused by a pathogen. Go to S4.4.1.

  9. An adult has a mass of 70 kg and a height of 1.75 m. What is the BMI, to one decimal place?

    See the answer

    22.9

    1.75 × 1.75 = 3.0625. 70 ÷ 3.0625 = 22.9.

  10. An adult has a BMI of 27.5. Which band is this: underweight, healthy weight, overweight or obese?

    See the answer

    overweight

    27.5 is from 25 up to 30, which is the overweight band.

  11. An adult is 1.60 m tall. What mass, to the nearest whole kilogram, gives a BMI of 25?

    See the answer

    about 64 kg

    BMI = mass ÷ height squared, so mass = BMI × height squared. 1.60 × 1.60 = 2.56. 25 × 2.56 = 64.

Keep it

Copy this into your exercise book.

Fatty deposits narrow the arteries that feed the heart. Saturated fat, salt, smoking, heavy drinking and little exercise raise the risk. BMI is mass in kilograms divided by height in metres squared. It cannot tell muscle from fat.

Draw: An artery with a fatty deposit narrowing the space for blood, with an arrow showing the blood flow.

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