Genetic Influence on Body Mass Index Variation in Adolescents: A Twin Study in Ibadan, Oyo State

Obesity and body mass index (BMI) variation have significant genetic underpinnings, with heritability estimates between 40 and 70 percent from global twin studies. Twin study designs effectively partition genetic and environmental contributions to complex phenotypic traits. This study estimated the heritability of BMI in adolescent twins attending secondary schools in Ibadan, Oyo State, South West Nigeria. Forty monozygotic (MZ) and 40 dizygotic (DZ) twin pairs aged 12 to 18 years were recruited from Twin registries and school enumerations. Zygosity was confirmed using a validated physical similarity questionnaire supplemented by ABO and Rh blood group concordance testing. Height and weight were measured under standardised conditions to calculate BMI. Classical twin model fitting was applied to partition variance into additive genetic (A), shared environmental (C), and non-shared environmental (E) components. Intraclass correlations were significantly higher in MZ than DZ pairs, supporting a substantial additive genetic component. Dietary and physical activity data collected via questionnaire demonstrated significant non-shared environmental influence as well. These findings establish a preliminary heritability estimate for BMI in Nigerian adolescents. Keywords: heritability, BMI, twin study, adolescents, Ibadan