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Exam questions · Biology · Homeostasis

Body Mass, BMI and Type 2 Diabetes

  • 6 exam questions
  • 17 marks
  • 9 quick checks
  1. 1 State [1 mark]

    State the equation used to calculate body mass index (BMI).

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    Model answer

    BMI = mass in kilograms divided by height in metres squared.

    Mark scheme

    • Mass (kg) divided by height (m) squared — 1 mark
  2. 2 Calculate [3 marks]

    A man has a mass of 95 kg and a height of 1.75 m. Calculate his BMI to 1 decimal place, and state which group he is in.

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    Model answer

    The height squared is 3.0625, and 95 divided by 3.0625 is 31.0, so he is in the obese group.

    Mark scheme

    • 1.75 squared is 3.0625 — 1 mark
    • 31.0 — 1 mark
    • Obese — 1 mark
  3. 3 Calculate [2 marks]

    A man has a waist circumference of 106 cm and a hip circumference of 100 cm. Calculate his waist to hip ratio, and state whether it shows a higher risk for a man.

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    Model answer

    His ratio is 1.06, which is above 0.90, so the risk is higher.

    Mark scheme

    • 1.06 — 1 mark
    • Above 0.90, so higher risk — 1 mark
  4. 4 Describe [2 marks]

    Describe the correlation between BMI and the percentage of adults with type 2 diabetes shown in the bar chart.

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    Model answer

    As the BMI increases, the percentage of adults with type 2 diabetes increases, from 2% for a BMI below 18.5 to 28% for a BMI of 40 and above. This is a positive correlation.

    Mark scheme

    • Percentage rises as the BMI rises — 1 mark
    • Data, such as 2% to 28% — 1 mark
  5. 5 Explain [3 marks]

    Explain why a high BMI does not always show that a person is at risk of type 2 diabetes.

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    Model answer

    BMI only uses the mass and the height. A person with a lot of muscle can have a high BMI but little fat, so the risk of type 2 diabetes may be low. The waist to hip ratio, which shows where the fat is stored, gives extra information.

    Mark scheme

    • BMI uses only mass and height — 1 mark
    • Muscle is not fat — 1 mark
    • Waist to hip ratio gives extra information — 1 mark
  6. 6 Evaluate [6 marks]

    Evaluate the evidence that a high body mass increases the risk of type 2 diabetes.

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    Model answer

    Large studies show a positive correlation, as the BMI rises, the percentage of people with type 2 diabetes also rises, for example from 3% to 28% in the data. There is also a possible mechanism, because excess body fat, particularly around the abdomen, makes the cells less sensitive to insulin. The waist to hip ratio shows a similar pattern, and people with type 2 diabetes who lose mass often improve their glucose control. However, a correlation does not prove a cause, because people with a high BMI may also have a poor diet or take little exercise, or carry genes that increase the risk. BMI also does not distinguish muscle from fat, so some people with a high BMI are not at risk. On balance the evidence for a link is strong, but a high mass is one risk factor among several.

    Mark scheme

    • Positive correlation, with data — 1 mark
    • Mechanism: insulin resistance — 1 mark
    • Supporting evidence, such as weight loss — 1 mark
    • Correlation is not cause — 1 mark
    • Other factors, such as diet, exercise and genes — 1 mark
    • BMI limits, or a balanced conclusion — 1 mark

Quick check

  1. 1

    What is the equation for BMI?

    1. AHeight divided by mass
    2. BMass multiplied by height
    3. CMass divided by height squared
    4. DMass plus height
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    C: Mass divided by height squared

    Mass in kg divided by height in m squared.

  2. 2

    A BMI of 32 is in which group?

    1. AUnderweight
    2. BHealthy
    3. COverweight
    4. DObese
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    D: Obese

    30 or more is obese.

  3. 3

    What is the BMI of a person with a mass of 60 kg and a height of 1.5 m?

    1. A40.0
    2. B26.7
    3. C18.5
    4. D90.0
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    B: 26.7

    60 divided by 2.25 is 26.7.

  4. 4

    What does the waist to hip ratio show?

    1. AWhere the fat is stored
    2. BThe height of a person
    3. CThe number of muscles
    4. DThe blood glucose
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    A: Where the fat is stored

    Where the fat is stored.

  5. 5

    A woman has a waist to hip ratio of 0.90. What does this show?

    1. AA lower risk
    2. BUnderweight
    3. CA higher risk
    4. DNo information
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    C: A higher risk

    It is above 0.85, so the risk is higher.

  6. 6

    What is the correlation between BMI and type 2 diabetes?

    1. ANegative
    2. BPositive
    3. CThere is no correlation
    4. DZero
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    B: Positive

    Positive: as the BMI rises, the risk rises.

  7. 7

    What does a correlation NOT prove?

    1. AThat there is a link
    2. BThat there is a pattern
    3. CThat data were collected
    4. DThat one factor causes the other
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    D: That one factor causes the other

    That one factor causes the other.

  8. 8

    Why is BMI limited as a measure of health?

    1. AIt does not distinguish between muscle and fat
    2. BIt needs a blood test
    3. CIt cannot be calculated
    4. DIt only works for children
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    A: It does not distinguish between muscle and fat

    It does not distinguish between muscle and fat.

  9. 9

    How does obesity increase the risk of type 2 diabetes?

    1. AIt stops the pancreas from working at all
    2. BIt can make cells less sensitive to insulin
    3. CIt destroys the immune system
    4. DIt makes the liver larger
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    B: It can make cells less sensitive to insulin

    Excess fat can make cells less sensitive to insulin.