title: Longitudinal assessment of food intake, fecal energy loss, and energy expenditure after Roux-en-Y gastric bypass surgery in high-fat-fed obese rats.
abstract: BACKGROUND
  The efficacy of Roux-en-Y gastric bypass (RYGB) surgery to produce weight loss has been well-documented, but few studies have measured the key components of energy balance, food intake, and energy expenditure longitudinally.
  
  
  METHODS
  Male Sprague-Dawley rats on a high-fat diet underwent either RYGB, sham operation, or pair feeding and were compared to chow-fed lean controls. Body weight and composition, food intake and preference, energy expenditure, fecal output, and gastric emptying were monitored before and up to 4 months after intervention.
  
  
  RESULTS
  Despite the recovery of initially decreased food intake to levels slightly higher than before surgery and comparable to sham-operated rats after about 1 month, RYGB rats maintained a lower level of body weight and fat mass for 4 months that was not different from chow-fed age-matched controls. Energy expenditure corrected for lean body mass at 1 and 4 months after RYGB was not different from presurgical levels and from all other groups. Fecal energy loss was significantly increased at 6 and 16 weeks after RYGB compared to sham operation, and there was a progressive decrease in fat preference after RYGB.
  
  
  CONCLUSIONS
  In this rat model of RYGB, sustained weight loss is achieved by a combination of initial hypophagia and sustained increases in fecal energy loss, without change in energy expenditure per lean mass. A shift away from high-fat towards low-fat/high-carbohydrate food preference occurring in parallel suggests long-term adaptive mechanisms related to fat absorption.
authors.affiliation: Neurobiology of Nutrition Laboratory, Pennington Biomedical Research Center, Louisiana State University, 6400 Perkins Road, Baton Rouge, LA 70808, USA.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Shin
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Zheng
authors.forename: R Leigh
authors.initials: RL
authors.lastname: Townsend
authors.forename: Laurel M
authors.initials: LM
authors.lastname: Patterson
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Holmes
authors.forename: Hans-Rudolf
authors.initials: HR
authors.lastname: Berthoud
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001823:Body Composition; D001835:Body Weight; D059305:Diet, High-Fat; D004195:Disease Models, Animal; D004435:Eating; D004734:Energy Metabolism; D005243:Feces; D005518:Food Preferences; D015390:Gastric Bypass / Q000379:methods*; D008297:Male; D009765:Obesity / Q000601:surgery*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015431:Weight Loss