title: The relative reinforcing value of food predicts weight gain in a longitudinal study of 7--10-y-old children.
abstract: BACKGROUND
  The relative reinforcing value (RRV) of food, defined as how hard an individual is prepared to work to gain access to food rather than a nonfood alternative, has been shown to be higher in obese adults and children than in their normal-weight counterparts. However, these cross-sectional studies are unable to determine whether a high RRV of food is predictive of adiposity change or whether it is a consequence of being obese.
  
  
  OBJECTIVE
  The objective was to examine the association between the RRV of food and 1-y weight gain in children aged 7-10 y.
  
  
  METHODS
  An observational longitudinal study design was used. The RRV of food was determined by using a questionnaire method at baseline when the children (n = 316) were aged 7-9 y. Adiposity [body mass index (BMI), BMI SD score, fat mass index, waist circumference, and waist circumference SD score] was assessed at baseline and after 1 y.
  
  
  RESULTS
  Regression analyses indicated that the RRV of food was not associated with any measure of adiposity at baseline or at the 1-y follow-up (all P > 0.58). Changes in BMI (B = 0.06, P < 0.001), BMI SD score (B = 0.03, P = 0.001), and fat mass index (B = 0.09, P = 0.001) after 1 y were significantly predicted by the RRV of food at baseline.
  
  
  CONCLUSIONS
  The RRV of food predicted the change in adiposity over a relatively short-term period of 1 y and thus may be associated with the development of obesity. The lack of association in cross-sectional analyses indicates that this behavior is a risk factor for weight gain, although weight differences may not emerge until later childhood.
authors.affiliation: Department of Epidemiology and Public Health, University College London, London, United Kingdom, and the Institute of Psychological Sciences, University of Leeds, Leeds, United Kingdom.
authors.forename: Claire
authors.initials: C
authors.lastname: Hill
authors.forename: Jenny
authors.initials: J
authors.lastname: Saxton
authors.forename: Laura
authors.initials: L
authors.lastname: Webber
authors.forename: John
authors.initials: J
authors.lastname: Blundell
authors.forename: Jane
authors.initials: J
authors.lastname: Wardle
mesh_terms: D050154:Adiposity / Q000502:physiology*; D001823:Body Composition; D015992:Body Mass Index; D002648:Child; D004435:Eating / Q000523:psychology*; D005260:Female; D005502:Food; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009765:Obesity / Q000453:epidemiology / Q000209:etiology* / Q000523:psychology*; D011237:Predictive Value of Tests; D012054:Reinforcement, Psychology; D011795:Surveys and Questionnaires; D055105:Waist Circumference; D015430:Weight Gain