The Efficacy of Energy-Restricted Diets in Achieving Preoperative Weight Loss for Bariatric Patients: a Systematic Review

Obes Surg. 2018 Nov;28(11):3678-3690. doi: 10.1007/s11695-018-3451-1.


In bariatric practice, a preoperative weight loss of at least 5% is recommended. However, the hypocaloric diets prescribed vary and no consensus exists. This study examined the efficacy of preoperative diets in achieving 5% weight loss. From a systematic literature search, eight randomised controlled trials (n = 862) were identified. Half of the trials used a "very-low-calorie diet" whilst the rest employed a "low-calorie diet". Only five diets achieved ≥ 5% weight loss over varying durations and energy intakes. By inference, compliance with a 700-1050 kcal (2929-4393 kJ) diet, consisting of moderate carbohydrate, high protein and low/moderate fat, for 3 weeks is likely to achieve 5% weight loss. A low-carbohydrate diet (< 20 g/day) may achieve this target within a shorter duration. Additional research is required to validate these conclusions.

Keywords: Bariatric surgery; Low-calorie diet; Metabolic surgery; Obesity; Very-low-calorie diet.

Publication types

  • Systematic Review

MeSH terms

  • Bariatrics
  • Caloric Restriction*
  • Combined Modality Therapy
  • Diet, Carbohydrate-Restricted
  • Diet, Fat-Restricted
  • Diet, Reducing*
  • Energy Intake
  • Humans
  • Obesity / diet therapy*
  • Obesity / surgery
  • Obesity, Morbid / surgery
  • Randomized Controlled Trials as Topic
  • Weight Loss*