Genetic risk for high BMI has grown more predictive as the obesity epidemic has unfolded, four-cohort study finds

A study published in PLOS Genetics on 18 June 2026, led by Liam Wright and colleagues at University College London and the University of Bristol, examines how the relationship between genetic predisposition to high body mass index (BMI) and observed BMI has shifted across generations as environmental conditions changed.

The researchers analysed data from 19,379 participants drawn from four well-established British birth cohorts, born in 1946, 1958, 1970, and approximately 2001 — spanning the period before and during the rise of the obesity epidemic. Polygenic indices (PGI) derived from genome-wide association studies of adult BMI were used to quantify each participant's inherited predisposition. BMI was measured at multiple time points between ages 3 and 69 years.

The analysis found that polygenic risk for high BMI was more strongly associated with observed BMI in later-born cohorts, suggesting that the obesogenic environment prevalent from the 1970s onwards has amplified the expression of genetic predispositions. The findings are consistent with gene-environment interaction models in which permissive environments allow genetic variation in appetite regulation, energy expenditure, and related pathways to translate more fully into phenotypic differences.

The study contributes to ongoing debate about the relative contributions of genetics and environment to rising obesity prevalence and is particularly relevant to researchers working on polygenic risk scores and gene-environment interaction, as well as to educators covering the quantitative genetics of complex traits. It was published open-access in PLOS Genetics.