Heritability and individual differences: Eating behaviour and weight

What is the heritability range of body weight?

50–90%.

What evidence shows weight is genetically influenced?

dentical (MZ) twins are much more similar in body weight than non‑identical (DZ) twins.

What were the TEDS heritability estimates for BMI and waist circumference at age 8–11?

• BMI SDS heritability = 0.77

• Waist circumference heritability = 0.76

How many genetic loci have been associated with BMI?

1000 loci.

Why can rising obesity rates NOT be explained by genetics alone?

The gene pool has not changed in 30 years — the environment must be responsible.

What is the “obesity paradox”?

Both genes and environment strongly determine obesity risk.

What factors contribute to an obesogenic food environment?

• High availability & variety

• Large portion sizes

• Low cost

• Advertising

• High energy density

What factors contribute to an obesogenic activity environment?

• Labour‑saving devices

• Sedentary travel

• Enjoyable sedentary activities

• High ambient temperatures

• Limited access to outdoor activity

What does Behavioural Susceptibility Theory (BST) propose?

Genes influence weight via appetite.

• genetic predisposition for appetite traits determines how someone responds to food environment

What are the two key appetite traits in BST?

• Food Responsiveness (FR) - extent to which you want to eat something in response to seeing or smelling food

• Satiety Sensitivity (SS) - the extent which you recognised the internal feelings of being full

Why are children ideal for appetite studies?

• Less dieting

• Less social desirability

• Less long‑standing obesity

• Enables cause–effect inference

How is appetite commonly measured in research?

Using the Child Eating Behaviour Questionnaire (CEBQ).

What study supports the high heritability of appetite?

The Gemini twin cohort — MZ twins showed much higher similarity in appetite traits than DZ twins.

What were the heritability values for appetite traits in the Gemini study?

• Food Responsiveness: 0.59

• Satiety Sensitivity: 0.72

How is appetite associated with weight in children?

• Higher SS → lower BMI & waist

• Higher FR → higher BMI & waist

From TEDS study

What does the meta‑analysis of 72 studies show?

• Food Responsiveness → consistently linked to higher body weight

• Satiety Sensitivity → consistently linked to lower body weight

How does appetite influence early weight gain?

Babies with bigger appetites gain more weight from birth to 15 months (~1 kg difference; 10%).

• casual relationship

Give an example of G×E interaction described in the lecture

Two genetically predisposed individuals:

• Healthy environment → genes NOT expressed

• Obesogenic environment → genes ARE expressed

How has the heritability of BMI changed over time

It has increased across birth cohorts during the obesity epidemic.

What did the Home Environment Inventory study (2018) find?

BMI heritability is higher in more obesogenic home environments.
(Genetic effect: 0.86 vs 0.39; Environmental effect: 0.14 vs 0.61)

• twins at 4 years own (gemini)

What is the key message summarised

Body weight results from genes interacting with the environment. People express genetic risk only in permissive (obesogenic) environments.