title: Diet-induced thermogenesis in postoperatve Roux-en-Y gastric bypass patients with weight regain.
abstract: BACKGROUND
  Bariatric surgery has been shown to be an effective treatment for obesity. Changes in energy expenditure, especially through diet-induced thermogenesis (DIT), have been identified as one of the mechanisms to explain this success. However, not all patients are able to maintain healthy postoperative weight loss. Therefore, a question arises: In the weight regain after bariatric surgery, are these changes in energy metabolism still active?
  
  
  OBJECTIVE
  To investigate if weight regain after Roux-en-Y gastric bypass (RYGB) surgery is associated with a lower diet-induced thermogenesis in the late postoperative period.
  
  
  METHODS
  A cross-sectional study with the participants chosen from among the patients from a private practice.
  
  
  METHODS
  This was a cross-sectional study where 3 groups of female patients were evaluated: (1) 20 patients with a RYGB postoperative time period of at least 2 years, who kept a healthy weight after surgery (loss of at least 50% of excess weight; Healthy group); (2) 19 patients with clinically severe obesity (BMI>40 kg/m(2), without co-morbidities and>35 kg/m(2), with co-morbidities; Pre group); (3) 18 patients who experienced weight regain after RYGB (Regain group). The 3 groups were submitted to indirect calorimetry to measure resting metabolic rate (RMR), respiratory quotient (RQ), and DIT. Immediately after the RMR measurement, a mixed meal of regular consistency was offered. Ten minutes after the food intake began, energy expenditure measurements were initiated continuing throughout the following 3 postprandial hours. Body composition was evaluated using multifrequency bioelectrical impedance. In subgroups of the studied population, glucose and insulin levels were measured at baseline and at 30, 60, 90, 120, and 180 minutes after feeding. The mean area under the curve (AUC) between the 3 groups and measurements at baseline were compared using the analysis of variance (ANOVA).
  
  
  RESULTS
  The Healthy group had the highest weight adjusted RMR value compared with both the Pre and Regain group (23.03±3.02 kcal/kg; 16.18±2.94 kcal/kg; 17.11±3.28 kcal/kg, respectively; P<.0001). The Regain and Pre groups showed no difference for this variable. The weight-adjusted DIT (AUC 0-180 min) was about 42% and 34% higher in the Healthy group compared with the Pre and Regain groups, respectively (P<.0001). Lean body mass (kg) showed a positive correlation with the AUC of weight-adjusted DIT in the 3 groups. Multiple regression revealed that lean body mass was the only variable related to weight adjusted DIT, independent of group and other selected variables.
  
  
  CONCLUSIONS
  Weight-adjusted DIT in the Regain group was smaller compared with the Healthy group, and with no difference compared with the Pre group. The lean body mass seems to have a positive association with diet-induced thermogenesis.
authors.affiliation: University of Brasília, Brasilia, Brazil; Gastrocirurgia Clinic, private practice, Brasilia, Brazil.
authors.forename: Mariane de Almeida
authors.initials: MA
authors.lastname: Cardeal
authors.affiliation: University of Brasília, Brasilia, Brazil; Gastrocirurgia Clinic, private practice, Brasilia, Brazil. Electronic address: silvialeitefaria@gmail.com.
authors.forename: Silvia Leite
authors.initials: SL
authors.lastname: Faria
authors.affiliation: Gastrocirurgia Clinic, private practice, Brasilia, Brazil.
authors.forename: Orlando Pereira
authors.initials: OP
authors.lastname: Faria
authors.affiliation: University of Brasília, Brasilia, Brazil.
authors.forename: Marcela
authors.initials: M
authors.lastname: Facundes
authors.affiliation: University of Brasília, Brasilia, Brazil.
authors.forename: Marina Kiyomi
authors.initials: MK
authors.lastname: Ito
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D004032:Diet; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D007328:Insulin / Q000378:metabolism; D009765:Obesity / Q000097:blood / Q000378:metabolism / Q000601:surgery*; D011182:Postoperative Care; D012008:Recurrence; D022722:Thermogenesis / Q000502:physiology*; D013851:Thinness / Q000503:physiopathology; D015430:Weight Gain / Q000502:physiology*
chemical_list: D001786:Blood Glucose; D007328:Insulin
keywords: Bariatric surgery; Diet-induced thermogenesis; Obesity; Resting metabolic rate; Roux-en-Y gastric bypass; Weight regain