title: Risk of symptomatic gallstones and cholecystectomy after a very-low-calorie diet or low-calorie diet in a commercial weight loss program: 1-year matched cohort study.
abstract: BACKGROUND
  Concern exists regarding gallstones as an adverse event of very-low-calorie diets (VLCDs; <800 kcal per day).
  
  
  OBJECTIVE
  To assess the risk of symptomatic gallstones requiring hospital care and/or cholecystectomy in a commercial weight loss program using VLCD or low-calorie diet (LCD).
  
  
  METHODS
  A 1-year matched cohort study of consecutively enrolled adults in a commercial weight loss program conducted at 28 Swedish centers between 2006 and 2009. A 3-month weight loss phase of VLCD (500 kcal per day) or LCD (1200-1500 kcal per day) was followed by a 9-month weight maintenance phase. Matching (1:1) was performed by age, sex, body mass index, waist circumference and gallstone history (n=3320:3320). Gallstone and cholecystectomy data were retrieved from the Swedish National Patient Register.
  
  
  RESULTS
  One-year weight loss was greater in the VLCD than in the LCD group (-11.1 versus -8.1 kg; adjusted difference, -2.8 kg, 95% CI -3.1 to -2.4; P<0.001). During 6361 person-years, 48 and 14 gallstones requiring hospital care occurred in the VLCD and LCD groups, respectively, (152 versus 44/10 000 person-years; hazard ratio, 3.4, 95% CI 1.8-6.3; P<0.001; number-needed-to-harm, 92, 95% CI 63-168; P<0.001). Of the 62 gallstone events, 38 (61%) resulted in cholecystectomy (29 versus 9; hazard ratio, 3.2, 95% CI 1.5-6.8; P=0.003; number-needed-to-harm, 151, 95% CI 94-377; P<0.001). Adjusting for 3-month weight loss attenuated the hazard ratios, but the risk remained higher with VLCD than LCD for gallstones (2.5, 95% CI 1.3-5.1; P=0.009) and became borderline for cholecystectomy (2.2, 95% CI 0.9-5.2; P=0.08).
  
  
  CONCLUSIONS
  The risk of symptomatic gallstones requiring hospitalization or cholecystectomy, albeit low, was 3-fold greater with VLCD than LCD during the 1-year commercial weight loss program.
authors.affiliation: Clinical Epidemiology Unit, Department of Medicine (Solna) Karolinska Institutet, Stockholm, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Johansson
authors.affiliation: Uppsala University, Department of Medical Sciences, Uppsala, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Sundström
authors.affiliation: Karolinska Institutet, Department of Clinical Science, Intervention and Technology (CLINTEC), Stockholm, Sweden.
authors.forename: C
authors.initials: C
authors.lastname: Marcus
authors.affiliation: Karolinska Institutet, Obesity Center, Department of Medicine, Stockholm, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Hemmingsson
authors.affiliation: Clinical Epidemiology Unit, Department of Medicine (Solna) Karolinska Institutet, Stockholm, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Neovius
mesh_terms: D000328:Adult; D031204:Caloric Restriction / Q000009:adverse effects*; D016022:Case-Control Studies; D002763:Cholecystectomy / Q000706:statistics & numerical data; D015331:Cohort Studies; D002149:Energy Intake; D005260:Female; D005500:Follow-Up Studies; D042882:Gallstones / Q000453:epidemiology / Q000209:etiology* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000178:diet therapy*; D018570:Risk Assessment; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors; D016896:Treatment Outcome; D015431:Weight Loss; D061217:Weight Reduction Programs