title: A twin study of differences in the response of plasma ghrelin to a milkshake preload in restrained eaters.
abstract: BACKGROUND
  Genetic, physiological, and psychological factors can affect food intake, but twin studies can distinguish inherited from environmental contributors. We examined the influence of attempted cognitive control of eating ("restrained eating") on levels of appetite-regulating hormones.
  
  
  METHODS
  Sixteen female, monozygotic twin pairs, discordant for Restraint Scale score (i.e., one twin a restrained eater with score>15 whereas the co-twin was unrestrained), were selected from the University of Washington Twin Registry. Serial plasma ghrelin concentrations were monitored during meals and a preload study paradigm involving intake of a milkshake followed by an ad libitum ice cream "taste test."
  
  
  RESULTS
  Body weight, body mass index, resting energy expenditure, and fasting leptin levels were very similar between restrained and unrestrained twins. In a preload study, twins ate similar amounts of ice cream shortly after drinking identical milkshakes (mean±SD; restrained 239±158 vs. unrestrained 228±132kcal; P=0.83). However, ghrelin concentrations during the preload study were significantly higher (P=0.03) in restrained twins than in their unrestrained co-twins. Regardless of restraint status, ghrelin levels prior to the preload study were prospectively and positively associated with ice cream intake (P=0.001).
  
  
  CONCLUSIONS
  Compared to their unrestrained co-twins, restrained twins had higher endogenous ghrelin levels during a preload study, but ate similar amounts. This finding is consistent with exertion of cognitive control relative to the state of physiologic appetite stimulation. Moreover, these findings in twins suggest that higher ghrelin levels result from restrained eating behavior and not from genetic predisposition.
authors.affiliation: Nutritional Sciences Program, University of Washington, School of Public Health, 305 Raitt Hall, Box 353410, Seattle, WA 98195, USA. Electronic address: rjm22@uw.edu.
authors.forename: Rachel
authors.initials: R
authors.lastname: Myhre
authors.affiliation: Department of Epidemiology, University of Washington School of Public Health, Box 357236, Seattle, WA 98195, USA; Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N. P.O. Box 19024, Seattle, WA 98109-1024, USA. Electronic address: mkratz@fhcrc.org.
authors.forename: Mario
authors.initials: M
authors.lastname: Kratz
authors.affiliation: Department of Epidemiology, University of Washington School of Public Health, Box 357236, Seattle, WA 98195, USA; Vietnam Era Twin Registry, VA Epidemiologic Research and Information Center, 1600S Columbian Way, Seattle, WA 98108, USA. Electronic address: goldie1@uw.edu.
authors.forename: Jack
authors.initials: J
authors.lastname: Goldberg
authors.affiliation: Department of Psychology, University of Toronto at Mississaugua, 3359 Mississaugua Road N. Mississaugua, Toronto, ON, Canada. Electronic address: jpolivy@utm.toronto.ca.
authors.forename: Janet
authors.initials: J
authors.lastname: Polivy
authors.affiliation: Division of General Internal Medicine, Department of Medicine, University of Washington School of Medicine, 325 Ninth Ave 359780, Seattle, WA 98104, USA. Electronic address: smelhorn@uw.edu.
authors.forename: Susan
authors.initials: S
authors.lastname: Melhorn
authors.affiliation: Department of Epidemiology, University of Washington School of Public Health, Box 357236, Seattle, WA 98195, USA. Electronic address: dedra@uw.edu.
authors.forename: Dedra
authors.initials: D
authors.lastname: Buchwald
authors.affiliation: Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, 1959 NE Pacific St Box 356426, Seattle, WA 98195-6426, USA. Electronic address: davidec@uw.edu.
authors.forename: David E
authors.initials: DE
authors.lastname: Cummings
authors.affiliation: Division of General Internal Medicine, Department of Medicine, University of Washington School of Medicine, 325 Ninth Ave 359780, Seattle, WA 98104, USA. Electronic address: ellschur@uw.edu.
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Schur
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D004435:Eating / Q000502:physiology; D002149:Energy Intake; D056344:Executive Function / Q000502:physiology*; D005215:Fasting / Q000097:blood; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D054439:Ghrelin / Q000097:blood*; D006801:Humans; D007054:Ice Cream; D020738:Leptin / Q000097:blood; D014430:Twins, Monozygotic; D055815:Young Adult
chemical_list: D054439:Ghrelin; D020738:Leptin
keywords: Appetite; Genetic; Ghrelin; Restrained eating