title: Neuropsychological assessment as a predictor of weight loss in obese adolescents.
abstract: BACKGROUND
  Obese individuals are known to be more impulsive than their normal-weight counterparts. Impulsivity has been postulated to be a predictor of weight loss.
  
  
  METHODS
  A pre-post study was designed to determine for the first time whether impulsivity changed with weight loss during a lifestyle and physical activity intervention programme lasting 2-8 weeks.
  
  
  METHODS
  Fifty-three obese adolescents with a body mass index (BMI) of 33.75 ± 7.9 attending a residential camp were tested and compared at baseline with 50 non-obese adolescents with a mean BMI of 20.6 ± 2.3.
  
  
  METHODS
  Inhibitory control was measured with the CANTAB (Cambridge Cognition, Cambridge, UK) Stop Signal Task. MATLAB (The Mathswork Inc., Natick, MA, USA) was used to measure the temporal discounting constant.
  
  
  RESULTS
  The obese group was more impulsive than the normal weight adolescents. BMI reduced significantly from 33.76 kg m(-2) to 30.93 kg m(-2) after completing camp. The stop signal reaction time (SSRT) decreased from 225.38 ± 94.22 to 173.76 ± 107.05 ms (n=47, P=0.0001). A reduction in inhibitory control during camp was predictive of those who showed the greatest reduction in BMI (Wilks' Lambda=0.9, F(1,50)=4.85, P=0.034). The number of weeks in camp (Wilks' Lambda=0.83, F(1,50)=9.826, P=0.003) and the age of the adolescents (Wilks' Lambda=0.87, F(1,50)=5.98, P=0.02) were significantly associated with a reduction in inhibitory control as measured by the SSRT. A longer stay in camp was associated with a greater reduction in SSRT (B=25.45, t=2.02, P=0.05). Increasing age had a significant moderating role in the reduction of inhibitory control (B=-0.3, t=-0.034, P=0.05). Temporal discounting for monetary reward also fell significantly during camp.
  
  
  CONCLUSIONS
  This study highlights the potential to identify those who are obese by using an easy-to-measure psychometric test. Furthermore, it is the first study to report a reduction in impulsivity and an improvement in well-being as part of a government-approved residential camp for obese adolescents. The potential mechanisms for change in impulsivity with weight are discussed.
authors.affiliation: Centre for Health Policy, Imperial College London, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Kulendran
authors.affiliation: Centre for Health Policy, Imperial College London, London, UK.
authors.forename: I
authors.initials: I
authors.lastname: Vlaev
authors.affiliation: Centre for Health Policy, Imperial College London, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Sugden
authors.affiliation: Centre for Health Policy, Imperial College London, London, UK.
authors.forename: D
authors.initials: D
authors.lastname: King
authors.affiliation: Centre for Health Policy, Imperial College London, London, UK.
authors.forename: H
authors.initials: H
authors.lastname: Ashrafian
authors.affiliation: 1] Centre for Health Policy, Imperial College London, London, UK [2] Department of Exercise and Obesity, Leeds Metropolitan University, Leeds, UK.
authors.forename: P
authors.initials: P
authors.lastname: Gately
authors.affiliation: Centre for Health Policy, Imperial College London, London, UK.
authors.forename: A
authors.initials: A
authors.lastname: Darzi
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D001521:Behavior Therapy; D015992:Body Mass Index; D002648:Child; D005260:Female; D006801:Humans; D007175:Impulsive Behavior; D008297:Male; D009483:Neuropsychological Tests; D063766:Pediatric Obesity / Q000150:complications / Q000503:physiopathology / Q000523:psychology* / Q000628:therapy*; D011237:Predictive Value of Tests; D012201:Reward; D040242:Risk Reduction Behavior; D015431:Weight Loss