Genetic and Environmental Influences on Eating Behavior - A Study of Twin Pairs Reared Apart or Reared Together

Abstract

This study examined the relative influence of genetic versus environmental factors on specific aspects of eating behavior. Adult monozygotic twins (22 pairs and 3 singleton reared apart, 38 pairs and 9 singleton reared together, age 18-76 years, BMI 17-43 kg/m²) completed the Three Factor Eating Questionnaire. Genetic and environmental variance components were determined for the three eating behavior constructs and their subscales using model-fitting univariate and multivariate analyses. Unique environmental factors had a substantial influence on all eating behavior variables (explaining 45-71% of variance), and most strongly influenced external locus for hunger and strategic dieting behavior of restraint (explaining 71% and 69% of variance, respectively). Genetic factors had a statistically significant influence on only 4 variables: restraint, emotional susceptibility to disinhibition, situational susceptibility to disinhibition, and internal locus for hunger (heritabilities were 52%, 55%, 38% and 50%, respectively). Common environmental factors did not statistically significantly influence any variable assessed in this study. In addition, multivariate analyses showed that disinhibition and hunger share a common influence, while restraint appears to be a distinct construct. These findings suggest that the majority of variation in eating behavior variables is associated with unique environmental factors, and highlights the importance of the environment in facilitating specific eating behaviors that may promote excess weight gain.

Keywords: Disinhibition; environment; heritability; hunger; obesity; restraint.

Fig. (1)

Path diagram of the univariate MZA/MZT GCE twin model. MZA, monozygotic twins reared apart; MZT, monozygotic twins reared together; G, genetic factors; C, common environmental factors; E, unique environmental factors; g, c, e are path coefficients; P₁, phenotype of twin 1; P₂, phenotype of twin 2. Circles represent latent (unmeasured) variables. Squares represent observed (measured) variables. Single-headed arrows represent hypothesized casual relationships between variables. Double-headed arrows represent correlation or covariance between variables [20].

Fig. (2)

Variance components from univariate GCE twin model for Eating Inventory constructs and subscales. G, genetic; C, common environmental; E, unique environmental; RES, restraint; Dieting, strategic dieting behavior; Self, attitude to self-regulation; Fat, avoidance of fattening foods; DIS, disinhibition; Habit, habitual susceptibility; Emotion, emotional susceptibility; Situation, situational susceptibility; HUN, hunger; Internal, internal locus; External, external locus. All variables have non-statistically significant C components and statistically significant E components. ^a Statistically significant G component.

Fig. (3)

Common pathway model path diagram of Eating Inventory constructs. G, genetic; C, common environmental; E, unique environmental. Rectangles represent observed variables, and the proportion of variance due to G, C and E (with 95% CI in parentheses) is printed in each rectangle. Circles represent latent or unmeasured variables. Single-headed arrows represent hypothesized casual relationships between variables. Double-headed arrows represent variance. Path coefficients are standardized parameter estimates and 95% confidence intervals are reported in parentheses. Darkened lines indicate statistically significant paths. Subscripts indicate variable or factor under influence.