Intersectional inequality in general and central obesity: cross-sectional UK Biobank study

Abstract Background People exist at a combination of different individual and neighbourhood deprivations. Each of these combinations may have a unique impact on health. However, little is known about the intersectional inequality of these combinations on general and central obesity, including when considering their demographics. This study aims to answer these questions. Methods The sample comprised 452,339 participants from the UK Biobank study. Individuals were grouped into 320 intersectional strata according to their household income, neighbourhood deprivation, sex, ethnicity and age. Linear and logistic multilevel analysis of individual heterogeneity and discriminatory accuracy was used to establish the total, additive and interactive inequality of body mass index (BMI), fat mass index (FMI), and waist to height ratio (WHtR), as well as the associated obesity classifications. Results 6.5%, 25.2% and 9.1% of the total variation in BMI, FMI and WHtR, respectively, was due to inequality between the strata. Of this, 26.5%, 3.5% and 22.0% is interactive. 79, 58 and 93 strata for BMI, FMI and WHtR demonstrate a significant interactive effect. We found some patterns; for example, affluent white women have an advantaged interactive effect, whilst deprived black women have a disadvantaged effect. Meanwhile men experience the inverse relationship. The relationship between individual and neighbourhood deprivation is not universally experienced by all strata. For example, black men living in areas of high deprivation have higher BMIs as their household income increases. Conclusions A large proportion of variation in general and central obesity is due to intersectional inequality, with up to 26.5% being interactive. It is important that these intersectional effects are considered when designing policy interventions to avoid policy failure, such as by focussing on groups with high total and interactive risk.