title: A twin study of self-regulatory eating in early childhood: estimates of genetic and environmental influence, and measurement considerations.
abstract: OBJECTIVE
  Children differ greatly in their ability to self-regulate food intake for reasons that are poorly understood. This laboratory-based twin study tested the genetic and environmental contributions to self-regulatory eating and body fat in early childhood.
  
  
  METHODS
  A total of 69 4-7 year-old same-sex twin pairs, including 40 monozygotic and 29 dizygotic pairs, were studied. Self-regulatory eating was operationalized as the percentage compensation index (COMPX%), assessed by a 'preload' challenge in which lunch intake was measured following a low- (3 kcal) or high-calorie (159 kcal) drink. Body fat indexes also were measured. The familial association for COMPX% was estimated by an intraclass correlation, and biometric analyses estimated heritability.
  
  
  RESULTS
  Children ate more at lunch following the low- compared with high-energy preload (P<0.001), although variability in COMPX% was considerable. Compensation was significantly poorer among African American and Hispanic compared with European American children, and among girls compared with boys. There was a familial association for self-regulatory eating (ρ = 0.23, P = 0.03) but no significant genetic component. In all, 22% of the variance in COMPX% was due to shared environmental 'household' factors, with the remaining variance attributable to child-specific 'unique' or 'random' environments. Poorer self-regulatory eating was associated with greater percent body fat (r = -0.21, P = 0.04).
  
  
  CONCLUSIONS
  Self-regulatory eating was influenced by environmental factors, especially those differing among siblings. The absence of a significant genetic effect may reflect the age of the sample or could be artifactual due to measurement issues that need to be considered in future studies.
authors.affiliation: Department of Nutrition, Gillings School of Global Pubic Health, University of North Carolina - Chapel Hill, Chapel Hill, NC 27599-7461, USA. mfaith@unc.edu
authors.forename: M S
authors.initials: MS
authors.lastname: Faith
authors.forename: A
authors.initials: A
authors.lastname: Pietrobelli
authors.forename: M
authors.initials: M
authors.lastname: Heo
authors.forename: S L
authors.initials: SL
authors.lastname: Johnson
authors.forename: K L
authors.initials: KL
authors.lastname: Keller
authors.forename: S B
authors.initials: SB
authors.lastname: Heymsfield
authors.forename: D B
authors.initials: DB
authors.lastname: Allison
mesh_terms: D001069:Appetite Regulation / Q000235:genetics / Q000502:physiology*; D001628:Beverages; D015992:Body Mass Index; D002648:Child; D002664:Child Nutritional Physiological Phenomena / Q000235:genetics / Q000502:physiology*; D002675:Child, Preschool; D015331:Cohort Studies; D004435:Eating / Q000502:physiology*; D002149:Energy Intake; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008297:Male; D012737:Sex Factors; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D055105:Waist Circumference