Key result
While individual fast-food consumption was associated with higher BMI, there was no significant association between within-pair differences in fast-food consumption and BMI among identical twins, indicating the relationship is largely driven by genetic factors.
Why the study?
Is fast-food consumption associated with higher body mass index in adult twins?
Cross-Sectional (n=1,338)
Is fast-food consumption associated with higher body mass index in adult twins?
Mean Difference: 0.16 (95% CI -0.05–0.37)
p-value: p=>0.05
The association between fast-food consumption and BMI appears to be largely confounded by shared genetic factors rather than a direct environmental effect, as evidenced by the lack of association within monozygotic twin pairs.
Genetic factors may confound the fast-food–BMI link observed in twins; leaves open causal effects on weight in broader populations.
Obesity is a substantial health problem in the United States, and is associated with many chronic diseases. Previous studies have linked poor dietary habits to obesity. This cross-sectional study aimed to identify the association between body mass index (BMI) and fast-food consumption among 669 same-sex adult twin pairs residing in the Puget Sound region around Seattle, Washington. We calculated twin-pair correlations for BMI and fast-food consumption. We next regressed BMI on fast-food consumption using generalized estimating equations (GEE), and finally estimated the within-pair difference in BMI associated with a difference in fast-food consumption, which controls for all potential genetic and environment characteristics shared between twins within a pair. Twin-pair correlations for fast-food consumption were similar for identical (monozygotic; MZ) and fraternal (dizygotic; DZ) twins, but were substantially higher in MZ than DZ twins for BMI. In the unadjusted GEE model, greater fast-food consumption was associated with larger BMI. For twin pairs overall, and for MZ twins, there was no association between within-pair differences in fast-food consumption and BMI in any model. In contrast, there was a significant association between within-pair differences in fast-food consumption and BMI among DZ twins, suggesting that genetic factors play a role in the observed association. Thus, although variance in fast-food consumption itself is largely driven by environmental factors, the overall association between this specific eating behavior and BMI is largely due to genetic factors.
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Cohen‐Cline et al. (2015) conducted a cross-sectional in Obesity (n=1,338). Fast-food consumption vs. Lower or no fast-food consumption was evaluated on Within-pair difference in BMI associated with a 1-meal/week difference in fast-food consumption (fully adjusted model) (MD 0.16, 95% CI -0.05, 0.37, p=>0.05). While individual fast-food consumption was associated with higher BMI, there was no significant association between within-pair differences in fast-food consumption and BMI among identical twins, indicating the relationship is largely driven by genetic factors.
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