Aim:

We propose to go beyond prevalence-based methods to test the relationship between obesity and parental income amongst children and investigate the differences by race/ethnicity and gender.

Hypotheses:

1. a)Using Unconditional Quantile Regression (Joliffee 2011) with BMI Z-scores the independent variable, low socio-economic status will be associated with greater weight at the overweight and obese BMI Z-score thresholds.

b)When accounting for parental weight status (overweight or obese), the coefficient for the effect of income on child BMI Z-scores at the overweight and obese thresholds will be reduced

c) Comparing Ordinary Least Squares estimates for the effect of parental weight status and income on child BMI Z-scores will underestimate the effect at the overweight and obese thresholds.

2. a) The net concentration index for measures of child obesity will be negative

b) A significant proportion of the concentration index for measures of child obesity will be explained by parental and weight status. Including parental obesity status will reduce the independent effect of income on obesity status for children.

The results of this analysis has policy implications. If the coefficient is significant after controlling for parental obesity status, this may indicate that healthy weight initiatives should target poor children. If, however, the coefficient becomes insignificant, policies should target all children and particularly children with overweight or obese parents.

Exposure variables:

Income, parental weight status

Outcome variable:

BMI z-score (calculated using weight, height, gender and age)

Confounding variables:

Socioeconomic measures such as ethnicity, lifestyle behaviours including diet, TV viewing, physical activity, tobacco use, and sleep duration.

Reference List:

Jolliffe, D. (2011). Overweight and poor? On the relationship between income and the body mass index. Economics & Human Biology, 9, 342-355.