title: The contribution of malabsorption to the reduction in net energy absorption after long-limb Roux-en-Y gastric bypass.
abstract: BACKGROUND
  Roux-en-Y gastric bypass (RYGB) restricts food intake, and when the Roux limb is elongated to 150 cm, the procedure is believed to induce malabsorption.
  
  
  OBJECTIVE
  Our objective was to measure total reduction in intestinal absorption of combustible energy after RYGB and the extent to which this was due to restriction of food intake or malabsorption of ingested macronutrients.
  
  
  METHODS
  Long-limb RYGB was performed in 9 severely obese patients. Dietary intake and intestinal absorption of fat, protein, carbohydrate, and combustible energy were measured before and at 2 intervals after bypass. By using coefficients of absorption to measure absorptive function, equations were developed to calculate the daily gram and kilocalorie quantities of ingested macronutrients that were not absorbed because of malabsorption or restricted food intake.
  
  
  RESULTS
  Coefficients of fat absorption were 92 ± 1.3% before bypass, 72 ± 5.5% 5 mo after bypass, and 68 ± 8.7% 14 mo after bypass. There were no statistically significant effects of RYGB on protein or carbohydrate absorption coefficients, although protein coefficients decreased substantially in some patients. Five months after bypass, malabsorption reduced absorption of combustible energy by 124 ± 57 kcal/d, whereas restriction of food intake reduced energy absorption by 2062 ± 271 kcal/d. Fourteen months after bypass, malabsorption reduced energy absorption by 172 ± 60 kcal/d compared with 1418 ± 171 kcal/d caused by restricted food intake.
  
  
  CONCLUSIONS
  On average, malabsorption accounted for ≈6% and 11% of the total reduction in combustible energy absorption at 5 and 14 mo, respectively, after this gastric bypass procedure.
authors.affiliation: Baylor University Medical Center, Dallas, TX 75246, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Odstrcil
authors.forename: Juan G
authors.initials: JG
authors.lastname: Martinez
authors.forename: Carol A
authors.initials: CA
authors.lastname: Santa Ana
authors.forename: Beiqi
authors.initials: B
authors.lastname: Xue
authors.forename: Reva E
authors.initials: RE
authors.lastname: Schneider
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Steffer
authors.forename: Jack L
authors.initials: JL
authors.lastname: Porter
authors.forename: John
authors.initials: J
authors.lastname: Asplin
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Kuhn
authors.forename: John S
authors.initials: JS
authors.lastname: Fordtran
mesh_terms: D000328:Adult; D001466:Barium Sulfate / Q000032:analysis; D015992:Body Mass Index; D049628:Body Size; D003920:Diabetes Mellitus / Q000453:epidemiology; D004044:Dietary Proteins / Q000378:metabolism; D004386:Duodenum / Q000033:anatomy & histology; D004435:Eating / Q000502:physiology; D002149:Energy Intake; D004734:Energy Metabolism; D005243:Feces / Q000737:chemistry; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects* / Q000379:methods; D006801:Humans; D006859:Hydrogen / Q000032:analysis; D007408:Intestinal Absorption; D008286:Malabsorption Syndromes / Q000453:epidemiology / Q000209:etiology* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009584:Nitrogen / Q000378:metabolism; D009767:Obesity, Morbid / Q000503:physiopathology / Q000601:surgery*; D009929:Organ Size; D012143:Respiratory Physiological Phenomena; D016482:Urinalysis
chemical_list: D004044:Dietary Proteins; D001466:Barium Sulfate; D006859:Hydrogen; D009584:Nitrogen