Body Size and Obesity Across The Life Course

Question 1

What are the different stages of body size across age?

Answer 1

• Prenatal growth (size at birth as a proxy marker)
• Growth in infancy and childhood (pre- & post-puberty)
• Early adulthood to middle and old age

Question 2

Give examples of how the pattern of growth can differ?

Answer 2

• In final size
• Growth rate
• Puberty timing

Question 3

How do height trajectories differ?

Answer 3

• Individuals
• Sub-groups (e.g. by sex or ethnicity) populations
• Time periods (secular trends)

Question 4

What are the influences on height?

Answer 4

Height is the joint product of genetic and environmental
influences.

Question 5

What is health an important marker of?

Answer 5

Nutritional status and health in early life.

Question 6

Why did height steadily increase in 19th and 20th centuries?

Answer 6

As living standards improved and parents became taller.

Question 7

Give examples of environmental factors of height.

Answer 7

• Maternal smoking in pregnancy
• Breastfeeding
• Childhood illness
• Diet
• Socioeconomic factors

Question 8

Why is the proportion of environmental exposures affecting height more likely to be greater in poorer countries?

Answer 8

There are larger socio-economic differences and lower height heritability.

Question 9

Is adult short stature a risk factor for health
outcomes?

Answer 9

It is only indirectly a risk factor as adult height does not change once attained.

Question 10

What is the association between the timing of puberty and bone health later in life?

Answer 10

Later puberty associated with worse bone health at age 60.

Question 11

What is health trajectory affected by?

Answer 11

• Size (adult height)
• Timing of puberty
• Intensity (growth rate)

Question 12

What is the best marker of child growth?

Answer 12

Size

Question 13

List measures of adiposity.

Answer 13

• Weight and height
• Body Mass Index (BMI)
• Ponderal Index (PI)
• Body composition
• Anthropometry
• Laboratory methods
• Fat Mass

Question 14

Define adiposity.

Answer 14

The state of being fat; obesity.

Question 15

How is body composition measured?

Answer 15

Weight = lean mass + fat mass

Question 16

How does anthropometry measure adiposity?

Answer 16

• Meausring skinfold thickness at particular sites, e.g. triceps, biceps - regional adiposity
• Measuring waist circumference and hip circumference – central adiposity

Question 17

Give examples of laboratory methods that are used to measure adiposity.

Answer 17

• 4-compartment model
• deuterium dilution
• DEXA
• Bioelectric impedance

Question 18

Why is fat mass hard to measure?

Answer 18

Need to accurately split weight into fat and lean compartments.

Question 19

How is BMI related to FMI and LMI?

Answer 19

BMI = FMI + LMI

Question 20

What is the correlation between BMI and FMI?

Answer 20

High correlation at all ages and both sexes and a consistent slope.

Question 21

Is BMI poor or good at predicting FMI?

Answer 21

Poor

Question 22

What is the trend through the average life course in child-adult BMI?

Answer 22

Rapid increase in 1st year, decreases after infancy, reaches a minimum, increases through adolescence and into middle age.

Question 23

What is the adiposity rebound?

Answer 23

The second rise in body mass index (BMI) that occurs between 3 and 7 years.

Question 24

Why is the age of adiposity rebound (AR) a critical period for development of obesity?

Answer 24

Early AR is associated with higher BMI in adolescence and
early adulthood.

Question 25

BMI is imperfect as an index of obesity, why is it still used?

Answer 25

It’s useful and convenient and too entrenched worldwide to change it.

Question 26

What are the 3 mean BMI trajectory groups for males?

Answer 26

• ‘Normal’ (80.4%, lowest BMI & % of obesity all 3 ages)
• ‘High, increasing’ (6.4%, intermediate BMI, increased
  rapidly with age)
• ‘High, declining’ (13.1%, highest BMI, decreased with age)

Question 27

What are the influences on BMI trajectories?

Answer 27

• Parental BMI
• Maternal smoking during pregnancy
• Socio-economic position

Question 28

How do we calculate unadjusted for sequencing?

Answer 28

Log 𝑃(𝑜𝑏𝑒𝑠𝑒) divided by 1−𝑃(𝑜𝑏𝑒𝑠𝑒) = a + b multiplied by (maternal smoking)

Question 29

How do we calculate adjusted for sequencing?

Answer 29

Log 𝑃(𝑜𝑏𝑒𝑠𝑒) divided by 1−𝑃(𝑜𝑏𝑒𝑠𝑒) = a + b multiplied by (maternal smoking) + c multiplied by (maternal BMI)