Very low caloric diet before bariatric surgery reduces perioperative complications

July 16, 2021

Bariatric surgery is considered the most effective and durable modality of weight loss for patients living with class 2 and class 3 obesity. Safety concerns during the earlier days of bariatric surgery have been overcome by the introduction of laparoscopy and minimally invasive techniques into the field. Currently, bariatric surgery is as safe as cholecystectomy, appendectomy or hip replacement with a mortality rate as low as 0.1% to 0.3%.

"While the utilization of laparoscopy played a significant role in achieving such a safety profile, patient selection and preoperative optimization remain as essential," says Omar M. Ghanem, M.D., Endocrine and Metabolic Surgery at Mayo Clinic in Rochester, Minnesota. "Various risk stratification strategies have been developed to evaluate the factors associated with higher perioperative bariatric surgery complications."

Along the same line, investigators have assessed the usefulness of the very low caloric diet (VLCD) before metabolic surgery. A systematic review published in Surgery for Obesity and Related Diseases in 2018 included 849 patients from nine studies, three of which were randomized controlled trials. The authors reported that VLCD led to a significant preoperative weight loss (-2.4 to -14.8 kg) and a reduction of up to 20% in liver volume.

Additionally, in a randomized controlled trial published in Archives of Surgery (now JAMA Surgery) in 2011 comparing patients undergoing laparoscopic Roux-en-Y gastric bypass after VLCD to a control group, a reduction of the 30-day complication rate was noted after two weeks of VLCD. This multicentered study included a total of 294 patients. There were 18 complications recorded in the control group versus eight complications in the VLCD group at 30 days (p = 0.04).

This growing evidence on VLCD usefulness incited the bariatric surgery work group at Mayo Clinic in Minnesota to develop a preoperative bariatric two-week, low-caloric dietary regimen.

"The objective of the VLCD is multileveled," explains Tara M. Schmidt, M.Ed., RDN, LD, Clinical Nutrition, at Mayo Clinic in Minnesota. "Patients have a 'kick-off' weight loss prior to surgery, which is an encouraging start for most. Moreover, while this plan is not in any way meant to assess compliance, this diet helps patients realize the commitment they have to the bariatric surgery process. Ultimately, surgeons may benefit intraoperatively from the reduced liver size, especially in the left lobe, reduction in the mesenteric fat volume or both."

The VLCD plan

The VLCD plan comprises high-protein, low-carbohydrate-content shakes consumed multiple times a day.

Schmidt clarifies: "The bariatric surgery work group decided on an average of 100 to 120 grams of proteins, 100 to 135 grams of carbohydrates and a total of 800 to 1,000 kilocalories for the Rochester VLCD protocol. Hydration continues to be crucial; a minimum of two liters of fluids is required. Sports drinks and broth have been added to the plan to decrease the risk of hyponatremia previously seen in similar protocols.

"Special care needs to be taken for patients who are on hypoglycemic agents, insulin or both, to avoid any risks of hypoglycemia. A modification to this dietary plan was made to patients with chronic kidney disease, patients with a solitary kidney, or patients who are post-kidney transplant, to reduce kidney injury incidence."

"Patient compliance with all of these recommendations is fundamental," summarizes Dr. Ghanem, "thus, a thorough explanation of the protocol to the patient, conducted by a bariatric surgery team staff member, is essential."

For more information

Holderbaum M, et al. Effects of very low calorie diets on liver size and weight loss in the preoperative period of bariatric surgery: A systematic review. Surgery for Obesity and Related Diseases. 2018;14:237.

Van Nieuwenhove Y, et al. Preoperative very low-calorie diet and operative outcome after laparoscopic gastric bypass: A randomized multicenter study. JAMA Surgery. 2011;146:1300.