title: Factors influencing energy intake and body weight loss after gastric bypass.
abstract: OBJECTIVE
  The gastric bypass-induced quantitative and qualitative modifications of energy intake (En In, kcal/day) and their impact on body weight (bw) loss were evaluated. The factors influencing energy intake and body weight loss were also investigated.
  
  
  METHODS
  Longitudinal study.
  
  
  METHODS
  University Hospital of Geneva.
  
  
  METHODS
  Fifty obese women undergoing a Roux-en-Y gastric bypass.
  
  
  RESULTS
  The reduction of EnIn was significantly related to bw loss expressed either in kg or as percentage correction of excess bw (P<0.01 for both), whereas the post-operative modifications of diet composition did not play a role. Age and initial bw significantly influenced bw loss (P<0.0001 and P<0.001, respectively), as shown by multiple regression analysis. Patients were divided into four sub-groups according to their age (under or over 35 y) and initial bw (under or over 120 kg). ANOVA showed that under 35-y-old subjects reduced their EnIn significantly more than their older counterparts having similar bw (P<0.02 and P<0.05); consequently, bw loss, expressed in kg, was significantly (P<0.0001 and P<0.0005) larger in younger patients. Subjects with an initial bw over 120 kg lost significantly (P<0.001 and P<0.02) more weight as compared to patients with a smaller degree of obesity (under 120 kg) and similar age.
  
  
  CONCLUSIONS
  Gastric bypass-induced body weight loss is mainly due to the reduction of EnIn, whereas the qualitative modifications of the diet do not play a role. Younger subjects have a greater capacity to reduce EnIn and, therefore, lose more weight. Pre-operative high degree of obesity leads to a larger weight reduction, probably because of a greater energy deficit.
authors.affiliation: Division of Therapeutic Education for Chronic Diseases, Geneva University Hospital, Geneva, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Bobbioni-Harsch
authors.forename: O
authors.initials: O
authors.lastname: Huber
authors.forename: Ph
authors.initials: P
authors.lastname: Morel
authors.forename: G
authors.initials: G
authors.lastname: Chassot
authors.forename: T
authors.initials: T
authors.lastname: Lehmann
authors.forename: M
authors.initials: M
authors.lastname: Volery
authors.forename: E
authors.initials: E
authors.lastname: Chliamovitch
authors.forename: C
authors.initials: C
authors.lastname: Muggler
authors.forename: A
authors.initials: A
authors.lastname: Golay
mesh_terms: D000328:Adult; D000367:Age Factors; D000713:Anastomosis, Roux-en-Y; D015992:Body Mass Index; D002149:Energy Intake / Q000502:physiology*; D004734:Energy Metabolism; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D008137:Longitudinal Studies; D009767:Obesity, Morbid / Q000601:surgery* / Q000628:therapy; D013270:Stomach / Q000502:physiology / Q000601:surgery; D015431:Weight Loss / Q000502:physiology*