Nutrition Management in Bariatric Surgery
Manual of Clinical Nutrition Management B- 22 Copyright © 2013 Compass Group, Inc.
Medical Nutrition Therapy and Nutrition Intervention After Bariatric Surgery
Guidelines are based on scientific evidence and emerging evidence from bariatric centers and institutions
that specifically provide management and treatment for gastric bypass patients (1). The meal plan must be
individualized based on the type of surgery performed, postoperative stage, and individual tolerance to
volume and consistency of food. The dietitian should closely monitor patients for nutrition-related signs and
symptoms that may indicate vitamin, mineral, or protein deficiencies; meal planning problems; and problems
meeting weight loss goals (1,5). Nutrition diagnoses are common in patients following any gastric bypass
surgery due to the malabsorptive process used to achieve weight loss.
Energy requirements: An objective estimation of the required total energy is difficult due to the rapid
weight loss and rapid changes in the ratio of fat-free mass to fat mass. One study evaluated changes in the
measured resting energy expenditure after Roux-en-Y gastric bypass for severe obesity. The measured
resting energy expenditure was significantly less than the Harris-Benedict–predicted resting energy
expenditure before the operation, but it increased to the predicted value by 6 weeks postoperatively and
remained so during the 24-month evaluation period (14). The measured resting energy expenditure of
patients who were hypometabolic before surgery (defined as a measured resting energy expenditure less
than 15% the Harris-Benedict–predicted resting energy expenditure) increased significantly despite
reductions in energy intake (14). Daily energy intake was approximately 2,603 kcal before surgery for all
subjects and fell to an average of 815 kcal at 3 months, 969 kcal at 6 months, 1,095 kcal at 12 months, 1,259
kcal at 18 months, and 1,373 kcal at 24 months postoperatively (14). Total energy requirements of the
Bariatric Diet will not meet predicted or measured energy requirements in most cases and will depend on the
postoperative stage and volume of foods consumed by the patient. The goal of the diet is energy deficit to
promote substantial weight loss. As energy intake increases, the rate of weight loss generally decreases or
plateaus (1).
Protein requirements: Most programs recommend that at least 25% of the total energy intake should be
from protein to minimize lean muscle loss during rapid weight loss, build new tissue after surgery, and
maintain lean muscle tissue long term (1). During energy restriction, patients should consume 60 to 120
g/day of high-quality protein (1,15) or 1.5 g/kg of ideal body weight (5). Protein malnutrition is common in
biliopancreatic diversion surgeries and increases to 17.8% if the pouch volume is less than 200 mL (5).
Patients with biliopancreatic diversion or biliopancreatic diversion with duodenal switch procedures require
the higher end of the protein range with a minimum consumption of 80 g/day (1). Patients who ingest too
little protein (<40 g/day) or protein that is mostly low biological quality are at risk of developing ventricular
arrhythmias (16). Consuming adequate sources of high–biological value protein at each meal and snack is
suggested. One to 2 weeks after surgery, high-protein liquids that provide at least 15 g of protein per 8-oz
serving with less than 20 g of total carbohydrate and less than 5 g of fat are suggested (5). Foods such as
regular (not reduced sugar) Carnation Instant BreakfastTM, EnsureTM, Slim FastTM, and BoostTM may not meet
these criteria and should be avoided (5). Once solid foods are tolerated (generally 4 to 6 weeks after surgery),
foods that are low in fat and high in protein, such as lean red meat or pork, chicken, or turkey without the
skin, fish, eggs, and cottage cheese, are good protein sources. Modular protein supplements may be required
during the first 6 postoperative months until solid food intake is sufficient to meet the requirements,
especially since meat and dairy products are some of the most frequently reported food intolerances after
surgery (17). The protein digestibility corrected amino acid score for the evaluation of protein quality should
be assessed for patients who are dependent on supplements for a large percentage of their protein intake.
This score reflects the overall quality of a protein, because it represents the relative adequacy of the most
limiting amino acid (18). The practitioner must review the amino acid composition of the patient’s selected
commercial protein-products to ensure that they include adequate amounts of all limiting amino acids (18).
Patients should be carefully monitored and evaluated for symptoms of protein deficiency and protein-energy
malnutrition. Hair loss is an indicator of inadequate protein intake and can be a side effect of gastric bypass
procedures (1). (Refer to the discussion of Medical Complications and Nutrition Evaluation and Monitoring
Following Bariatric Surgery for additional information.)
Fat: Fat should provide approximately 25% to 30% of total energy. Fat may be difficult to digest or tolerate
after gastric bypass surgery, especially fried foods and snack foods. Steatorrhea is often a complication of the
biliopancreatic diversion and biliopancreatic diversion with duodenal switch procedures. Too much fat can
delay gastric emptying and cause reflux leading to heartburn. After bariatric surgery, all patients are at
increased risk for gallstone formation due to the rapid weight loss (1). Small amounts of dietary fat consumed