title: Energy expenditure and weight regain in patients submitted to Roux-en-Y gastric bypass.
abstract: BACKGROUND
  Although Roux-en-Y gastric bypass (RYGBP) is a highly effective treatment for clinically severe obesity, not all patients achieve desirable weight loss and maintenance. There is some evidence that weight loss can induce a disproportionate reduction in resting metabolic rate (RMR). This reduction in RMR can be related to fat-free mass (FFM) loss, as FFM is the greatest responsible for variations in energy expenditure at rest. Abnormally low basal metabolic rate may predispose surgical patients to weight regain.
  
  
  METHODS
  Thirty-six individuals were divided into two groups: patients who have kept a healthy weight 2 years after surgery and patients who showed weight regain of at least 2 kg 2 years after the surgery. Selected patients have signed a consent form. Body mass index and excess weight loss were evaluated. RMR and body fat percentage were measured. FFM is a heterogeneous component that can be partitioned into muscle mass and no-muscle mass. The FFM was calculated as the result of subtracting total fat weight from total body weight in kilogram. We also wanted to know if the predictive formulas to assess RMR overestimate energy expenditure in these patients. Statistical tests were used to analyze the two groups.
  
  
  RESULTS
  We found out that the RMR of the weight regain group was statistically inferior to the mean of the healthy weight group-the difference between the two groups was about 260 kcal/day. We also found out that the predictive formulas overestimate the RMR in the weight regain group.
  
  
  CONCLUSIONS
  This study suggests that a lower RMR may contribute to weight regain in patients who undergo RYGBP. It is important to ensure ways to elevate energy expenditure in the patient, such as increasing the percentage of fat-free mass in the body and the practice of physical activities.
authors.affiliation: Gastrocirurgia de Brasília/Gastronutrição Bariátrica, Brasília, Brazil. silvialeitefaria@brturbo.com.br
authors.forename: Silvia Leite
authors.initials: SL
authors.lastname: Faria
authors.forename: Emily
authors.initials: E
authors.lastname: Kelly
authors.forename: Orlando P
authors.initials: OP
authors.lastname: Faria
mesh_terms: D000328:Adult; D000465:Algorithms; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004734:Energy Metabolism; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects*; D006801:Humans; D008297:Male; D009767:Obesity, Morbid / Q000601:surgery*; D018579:Patient Selection; D016896:Treatment Outcome; D015430:Weight Gain; D015431:Weight Loss