Body Size and Obesity Across The Life Course Flashcards
What are the different stages of body size across age?
- Prenatal growth (size at birth as a proxy marker)
- Growth in infancy and childhood (pre- & post-puberty)
- Early adulthood to middle and old age
Give examples of how the pattern of growth can differ?
- In final size
- Growth rate
- Puberty timing
How do height trajectories differ?
- Individuals
- Sub-groups (e.g. by sex or ethnicity) populations
- Time periods (secular trends)
What are the influences on height?
Height is the joint product of genetic and environmental
influences.
What is health an important marker of?
Nutritional status and health in early life.
Why did height steadily increase in 19th and 20th centuries?
As living standards improved and parents became taller.
Give examples of environmental factors of height.
- Maternal smoking in pregnancy
- Breastfeeding
- Childhood illness
- Diet
- Socioeconomic factors
Why is the proportion of environmental exposures affecting height more likely to be greater in poorer countries?
There are larger socio-economic differences and lower height heritability.
Is adult short stature a risk factor for health
outcomes?
It is only indirectly a risk factor as adult height does not change once attained.
What is the association between the timing of puberty and bone health later in life?
Later puberty associated with worse bone health at age 60.
What is health trajectory affected by?
- Size (adult height)
- Timing of puberty
- Intensity (growth rate)
What is the best marker of child growth?
Size
List measures of adiposity.
- Weight and height
- Body Mass Index (BMI)
- Ponderal Index (PI)
- Body composition
- Anthropometry
- Laboratory methods
- Fat Mass
Define adiposity.
The state of being fat; obesity.
How is body composition measured?
Weight = lean mass + fat mass
How does anthropometry measure adiposity?
- Meausring skinfold thickness at particular sites, e.g. triceps, biceps - regional adiposity
- Measuring waist circumference and hip circumference – central adiposity
Give examples of laboratory methods that are used to measure adiposity.
- 4-compartment model
- deuterium dilution
- DEXA
- Bioelectric impedance
Why is fat mass hard to measure?
Need to accurately split weight into fat and lean compartments.
How is BMI related to FMI and LMI?
BMI = FMI + LMI
What is the correlation between BMI and FMI?
High correlation at all ages and both sexes and a consistent slope.
Is BMI poor or good at predicting FMI?
Poor
What is the trend through the average life course in child-adult BMI?
Rapid increase in 1st year, decreases after infancy, reaches a minimum, increases through adolescence and into middle age.
What is the adiposity rebound?
The second rise in body mass index (BMI) that occurs between 3 and 7 years.
Why is the age of adiposity rebound (AR) a critical period for development of obesity?
Early AR is associated with higher BMI in adolescence and
early adulthood.
BMI is imperfect as an index of obesity, why is it still used?
It’s useful and convenient and too entrenched worldwide to change it.
What are the 3 mean BMI trajectory groups for males?
- ‘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)
What are the influences on BMI trajectories?
- Parental BMI
- Maternal smoking during pregnancy
- Socio-economic position
How do we calculate unadjusted for sequencing?
Log 𝑃(𝑜𝑏𝑒𝑠𝑒) divided by 1−𝑃(𝑜𝑏𝑒𝑠𝑒) = a + b multiplied by (maternal smoking)
How do we calculate adjusted for sequencing?
Log 𝑃(𝑜𝑏𝑒𝑠𝑒) divided by 1−𝑃(𝑜𝑏𝑒𝑠𝑒) = a + b multiplied by (maternal smoking) + c multiplied by (maternal BMI)
