Skip to main content


Log in

Improving Compliance with Very Low Energy Diets (VLEDs) Prior to Bariatric Surgery—a Randomised Controlled Trial of Two Formulations

  • Original Contributions
  • Published:
Obesity Surgery Aims and scope Submit manuscript

A Correction to this article was published on 01 July 2019

This article has been updated



Preoperative very low energy diets (VLEDs) improve access during bariatric surgery. Compliance with traditional VLED is variable, mainly due to gastrointestinal side effects. Formulite™ is a new formulation of VLED, with higher protein, soluble fibre and probiotics.


To compare traditional VLED (Optifast™) with the new VLED (Formulite™) and assess compliance, weight loss, satisfaction, side effects and surgical access.


This was a randomised double-blinded study involving patients scheduled for bariatric surgery. The primary outcome was compliance, assessed by urinary ketone concentration and proportion of patients in ketosis at 2 weeks. Secondary outcomes were weight loss, satisfaction and patient reported outcomes, gastrointestinal side effects and operative conditions.


There were 69 participants: 35 in the Formulite™ group and 34 in the Optifast™ group. Ketosis at 2 weeks was achieved in both groups (88.5% vs 83.3%, Formulite™ vs. Optifast™, p = 0.602). Urinary ketones were higher with Formulite™ (1.5 vs 15 mmol/L, p = 0.030). Total body weight loss percentage, hunger and operative conditions were similar in both groups. Formulite™ produced less flatulence (score 3 vs 2, p = 0.010) and emotional eating (score 2 vs 1, p = 0.037); however, Optifast™ ranked higher in terms of taste (score 4 vs 3, p = 0.001) and overall satisfaction (score 5 vs 7, p = 0.011).


Compliance over 2 weeks was high in both VLEDs with most subjects achieving ketosis. Overall satisfaction was moderately high, although variable. Whilst Formulite™ is a viable alternative to Optifast™, better formulations of VLED that addresses key adverse effects, whilst achieving ketosis, would be of significant value.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Subscribe and save

Springer+ Basic
EUR 32.99 /Month
  • Get 10 units per month
  • Download Article/Chapter or Ebook
  • 1 Unit = 1 Article or 1 Chapter
  • Cancel anytime
Subscribe now

Buy Now

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2
Fig. 3

Similar content being viewed by others

Change history

  • 01 July 2019

    In the original article the name of author Alexandra Klejn was misspelled.


  1. Colles SL, Dixon JB, Marks P, et al. Preoperative weight loss with a very-low-energy diet: quantitation of changes in liver and abdominal fat by serial imaging. Am J Clin Nutr. 2006;84(2):304–11.

    Article  CAS  PubMed  Google Scholar 

  2. Alami RS et al. Is there a benefit to preoperative weight loss in gastric bypass patients? A prospective randomized trial. Surg Obes Relat Dis. 2007;3(2):141–5.

    Article  PubMed  Google Scholar 

  3. Gerber P, Anderin C, Thorell A. Weight loss prior to bariatric surgery: an updated review of the literature. Scand J Surg. 2015;104:33–9.

    Article  CAS  PubMed  Google Scholar 

  4. Faria SL, Faria OP, Cardeal MA, et al. Effects of a very low calorie diet in the preoperative stage of bariatric surgery: a randomized trial. Surg Obes Relat Dis. 2015;11:230–7.

    Article  PubMed  Google Scholar 

  5. Van Nieuwenhove Y et al. Preoperative very low-calorie diet and operative outcome after laparoscopic gastric bypass: a randomized multicenter study. Arch Surg. 2011;146(11):1300–5.

    Article  PubMed  Google Scholar 

  6. Glenn NM, Raine KD, Spence JC. Mandatory weight loss during the wait for bariatric surgery. Qual Health Res. 2015;25(1):51–61.

    Article  PubMed  Google Scholar 

  7. Formulite. Formulite Home Page. 2018 [cited 2018 19 Oct 2018]; Available from:

  8. Santesso N, Akl EA, Bianchi M, et al. Effects of higher-versus lower-protein diets on health outcomes: a systematic review and meta analysis. Eur J Clin Nutr. 2012;66:780–8.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  9. Dong JY, Zhang ZL, Wang PY, et al. Effects of high-protein diets on body weight, glycaemic control, blood lipids and blood pressure in type 2 diabetes: meta-analysis of randomised controlled trials. Br J Nutr. 2013;110:781–9.

    Article  CAS  PubMed  Google Scholar 

  10. Schwingshackl L, Hoffmann G. Long-term effects of low-fat diets either low or high protein on cardiovascular and metabolic risk factors: a systematic review and meta-analysis. Nutr J. 2013;12:48-2891-12-48.

    Article  CAS  Google Scholar 

  11. De Luis DA et al. Effects of a high-protein/low carbohydrate versus a standard hypocaloric diet on adipocytokine levels and insulin resistance in obese patients along 9 months. J Diabetes Complicat. 2015;29:950–4.

    Article  Google Scholar 

  12. Larsen TM, Dalskov SM, van Baak M, et al. Diets with high or low protein content and glycemic index for weight-loss maintenance. N Engl J Med. 2010;363:2102–13.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  13. Nagarajan N, Morden A, Bischof D, et al. The role of fiber supplementation in the treatment of irritable bowel syndrome: a systematic review and meta-analysis. Eur J Gastroenterol Hepatol. 2015;27:1002–10.

    Article  CAS  PubMed  Google Scholar 

  14. Moayyedi P, Quigley EMM, Lacy BE, et al. The effect of fiber supplementation on irritable bowel syndrome: a systematic review and meta-analysis. Am J Gastroenterol. 2014;109:1367–74.

    Article  CAS  PubMed  Google Scholar 

  15. Lewis MC et al. Changes in liver size and fat content after treatment with Optifast very low calorie diet. Obes Surg. 2006;16(6):697–701.

    Article  PubMed  Google Scholar 

  16. Edholm D, Kullberg J, Haenni A, et al. Preoperative 4-week low-calorie diet reduces liver volume and intrahepatic fat, and facilitates laparoscopic gastric bypass in morbidly obese. Obes Surg. 2011;21(3):345–50.

    Article  PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Wendy A. Brown.

Ethics declarations

Ethical Statement

Ethics approval was obtained from the Avenue Ethics Committee (ref no. 210). The trial was registered with the Australian Clinical Trials Register (ACTRN 12616001091493 at

Consent Statement

All participants provided written informed consent.

Conflict of Interest

The product Formulite™ was donated by the manufacturer for the purpose of this study.

Author 1: no conflicts of interest to declare.

Author 2: no conflicts of interest to declare.

Author 3: no conflicts of interest to declare.

Author 4: no conflicts of interest to declare.

Author 5: no conflicts of interest to declare.

Author 6: received a grant from the NHMRC, outside the submitted work.

Author 7: received grants from Johnson and Johnson, grants from Medtronic, grants from GORE, personal fees from GORE, grants from Applied Medical, grants from Apollo Endosurgery, grants and personal fees from Novo Nordisc, personal fees from Merck Sharpe and Dohme, outside the submitted work.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Davenport, L., Johari, Y., Klejn, A. et al. Improving Compliance with Very Low Energy Diets (VLEDs) Prior to Bariatric Surgery—a Randomised Controlled Trial of Two Formulations. OBES SURG 29, 2750–2757 (2019).

Download citation

  • Published:

  • Issue Date:

  • DOI: