Pre-operative Dietary Restriction for Patients Undergoing Bariatric Surgery in the UK: Observational Study of Current Practice and Dietary Effects

Very Low-Calorie Ketogenic Diet (VLCKD) as Pre-Operative First-Line Dietary Therapy in Patients with Obesity Who Are Candidates for Bariatric Surgery

Bariatric surgery is currently the most effective method for achieving long-term weight loss and reducing the risk of comorbidities and mortality in individuals with severe obesity. The pre-operative diet is an important factor in determining patients' suitability for surgery, as well as their post-operative outcomes and success in achieving weight loss. Therefore, the nutritional management of bariatric patients requires specialized expertise. Very low-calorie diets and intragastric balloon placement have already been studied and shown to be effective in promoting pre-operative weight loss. In addition, the very low-calorie ketogenic diet has a well-established role in the treatment of obesity and type 2 diabetes mellitus, but its potential role as a pre-operative dietary treatment prior to bariatric surgery has received less attention. Thus, this article will provide a brief overview of the current evidence on the very low-calorie ketogenic diet as a pre-operative dietary treatment in patients with obesity who are candidates for bariatric surgery.

Variation and outcomes of liver-reducing dietary regimens before bariatric surgery: a national retrospective cohort study

BACKGROUND

Liver-reducing diets (LRDs) are mandated prior to bariatric surgery, but there are no guidelines on their implementation.

OBJECTIVE

To establish the variation and effectiveness of LRDs utilized in clinical practice.

SETTING

A nationwide, multicenter, retrospective cohort study.

METHODS

A total of 1699 adult patients across 14 bariatric centers in the United Kingdom were included. Multilevel logistic regression models were developed to examine factors predictive of 5% weight loss.

RESULTS

Most centers (n = 9) prescribed an 800- to 1000-kcal diet, but the duration and formulation of diet was variable. Overall, 30.6% (n = 510) of patients achieved 5% weight loss during the LRD. After adjustment for preoperative weight, women had reduced odds (odds ratio [OR], .65; 95% confidence interval [CI], .48-.88; P = .005), while increasing age (OR, 1.01; 95% CI, 1.00-1.02; P = .043) and having type 2 diabetes (OR, 1.49; 95% CI, 1.16-1.92; P = .002) increased odds of 5% weight loss. A normal consistency food LRD (OR, .64; 95% CI, .42-.98; P = .041) and energy prescription of >1200 kcals/d (OR, .33; 95% CI, .13-.83; P = .019) reduced odds, while an LRD with a duration of 3 weeks (OR, 2.28; 95% CI, 1.02-5.09; P = .044) or greater increased odds of 5% weight loss.

CONCLUSIONS

There is wide variation in how LRDs are delivered in clinical practice, highlighting the need for an evidence-based consensus. Our findings suggest the optimal LRD before bariatric surgery contains 800 to 1200 kcals/d over a duration of 3 to 4 weeks. Further research is required to determine the optimal formulation of LRD and whether women may require a lower-energy LRD than men.

Expert opinion on the preoperative medical optimization of adults with diabetes undergoing metabolic surgery

Diabetes mellitus (DM) and obesity are interrelated in a complex manner, and their coexistence predisposes patients to a plethora of medical problems. Metabolic surgery has evolved as a promising therapeutic option for both conditions. It is recommended that patients, particularly those of Asian origin, maintain a lower body mass index threshold in the presence of uncontrolled DM. However, several comorbidities often accompany these chronic diseases and need to be addressed for successful surgical outcome. Laparoscopic Roux-en-Y gastric bypass (RYGB) and laparoscopic sleeve gastrectomy (LSG) are the most commonly used bariatric procedures worldwide. The bariatric benefits of RYGB and LSG are similar, but emerging evidence indicates that RYGB is more effective than LSG in improving glycemic control and induces higher rates of long-term DM remission. Several scoring systems have been formulated that are utilized to predict the chances of remission. A glycemic target of glycated hemoglobin < 7% is a reasonable goal before surgery. Cardiovascular, pulmonary, gastrointestinal, hepatic, renal, endocrine, nutritional, and psychological optimization of surgical candidates improves perioperative and long-term outcomes. Various guidelines for preoperative care of individuals with obesity have been formulated, but very few specifically focus on the concerns arising from the presence of concomitant DM. It is hoped that this statement will lead to the standardization of presurgical management of individuals with DM undergoing metabolic surgery.

Current preoperative strategies applied in the Dutch bariatric centers: A national survey

There is no consensus about the optimal management of patients undergoing bariatric surgery. This study aimed to identify current weight loss goals prior to bariatric surgery, as well as aimed to explore preoperative strategies related to diet, nutritional supplements and physical activity. An online survey was distributed among bariatric surgeons and dietitians in all 18 Dutch bariatric centers. This survey included the following four domains: weight loss, diet, nutritional supplements and physical activity. For the analyses one answer per center was used, either the most common answer or the answer given by the most expert responder. All 18 centers reported at least one response. Preoperative weight loss was requested in 28% of the centers, whereas 61% desired a stable weight or weight loss, and 11% had no requests. A preoperative diet was routinely recommended in 78% of the centers and on indication (ie, depending on baseline weight and/or comorbidity status) in 22%. The most frequently prescribed diet was a low-energy diet (800-1500 kcal/day) in 44% of the centers. Nutritional supplements were recommended in 78% of the centers. Physical activity with low intensity was recommended in 83% of the centers, while physical exercise training with mid- to high-intensity was recommended in 72%. Inconsistent responses within centers were observed in 56% of the questions. The current bariatric practice within the Netherlands shows high variability and inconsistencies in preoperative management. Consensus-building and standardization of strategies should be promoted in the future.

British Obesity and Metabolic Surgery Society Guidelines on perioperative and postoperative biochemical monitoring and micronutrient replacement for patients undergoing bariatric surgery-2020 update

Bariatric surgery is recognized as the most clinically and cost-effective treatment for people with severe and complex obesity. Many people presenting for surgery have pre-existing low vitamin and mineral concentrations. The incidence of these may increase after bariatric surgery as all procedures potentially cause clinically significant micronutrient deficiencies. Therefore, preparation for surgery and long-term nutritional monitoring and follow-up are essential components of bariatric surgical care. These guidelines update the 2014 British Obesity and Metabolic Surgery Society nutritional guidelines. Since the 2014 guidelines, the working group has been expanded to include healthcare professionals working in specialist and non-specialist care as well as patient representatives. In addition, in these updated guidelines, the current evidence has been systematically reviewed for adults and adolescents undergoing the following procedures: adjustable gastric band, sleeve gastrectomy, Roux-en-Y gastric bypass and biliopancreatic diversion/duodenal switch. Using methods based on Scottish Intercollegiate Guidelines Network methodology, the levels of evidence and recommendations have been graded. These guidelines are comprehensive, encompassing preoperative and postoperative biochemical monitoring, vitamin and mineral supplementation and correction of nutrition deficiencies before, and following bariatric surgery, and make recommendations for safe clinical practice in the U.K. setting.

The Optimal Nutritional Programme for Bariatric and Metabolic Surgery

PURPOSE OF REVIEW

Bariatric surgery is the most effective treatment for severe and complex obesity; however, the risk of developing nutrient deficiencies varies based upon the type of surgery, degree of malabsorption, and level of nutrition intervention. There are numerous factors that can impact the nutrition status of a patient during their pre- and postoperative journey. We review the critical components and considerations needed in order to provide optimal nutrition care for patients with bariatric surgery.

RECENT FINDINGS

A dietitian, specializing in bariatric surgery, is the best equipped healthcare provider to prepare and support patients in achieving and maintaining optimal nutrition status. We present best practices for both the pre- and postoperative nutrition-related phases of a patient's journey. The dietitian specialist is integral in the assessment and ongoing nutrition care of patients with bariatric surgery. Further consideration should be given to enable access for lifelong follow-up and monitoring.

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

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.

Dietary Management in the Immediate Preoperative Period of Bariatric Surgery: a National Overview : Bariatric Preoperative Diets

BACKGROUND

Although widely applied, there is no consensus about the characteristics of the diets prescribed in the immediate preoperative period of bariatric surgery (BS). The objective of this study was to perform a survey on preoperative dietary management in BS centers.

METHODS

This was a cross-sectional study with BS Brazilian centers. Only BS centers with certificate of excellence by Surgical Review Corporation were included. An electronic questionnaire was applied to assess details about the dietary management in the immediate preoperative period of BS.

RESULTS

Of the 15 centers invited, 80% (n = 12) answered the questionnaire. Preoperative weight loss was required to patients in all 12 centers. For 8.3% (n = 1), this request was applied to all patients; 91.7% (n = 11) of the centers requested weight loss in specific cases. Ten (83.3%) centers prescribed restrictive diets; none of these adopted a standard dietary protocol. The caloric value of the diets ranged from 800 to 2000 kcal/day. The duration of the diet ranged from 10 to 20 days in 40% (n = 4) of the centers and from 20 to 90 days in 60% (n = 6) of the centers. Dietary prescription was based on team consensus in 100% (n = 12) of the centers. In 33.3% (n = 4) of the centers, scientific evidence supporting dietary prescription was cited.

CONCLUSION

This study identified the frequent practice of requesting preoperative weight loss and the diversity of diets used in the immediate preoperative period by Brazilian BS centers. Future guideline proposal is needed on preoperative BS diets.

Bariatric Surgery Resistance: Using Preoperative Lifestyle Medicine and/or Pharmacology for Metabolic Responsiveness

Bariatric surgery is an effective and durable treatment for individuals with obesity and its associated comorbidities. However, not all patients meet weight loss and/or cardiometabolic goals following bariatric surgery, suggesting that some people are bariatric surgery resistant. The reason for this resistance is unclear, but potential factors, such as adiposity-derived inflammation, insulin resistance, hyperglycemia, and aerobic fitness prior to surgery, have been related to blunted surgery responsiveness. Exercise, diet, and/or pharmacology are effective at reducing inflammation and improving insulin action as well as physical function. Herein, we present data that supports the novel hypothesis that intervening prior to surgery can enhance disease resolution in people who are resistant to bariatric surgery.

Preoperative nutritional management of bariatric patients in Australia: The current practice of dietitians

AIM

The aim of this observational study was to investigate the reported practices of Australian dietitians managing bariatric surgery patients in the preoperative stage.

METHODS

An online survey of dietitians providing nutritional care to bariatric patients was developed for the purpose of this investigation. The survey questions were guided by the Clinical Practice Guidelines for the Perioperative Nutritional, Metabolic and Nonsurgical Support of the Bariatric Surgery Patient guidelines and current literature.

RESULTS

Ninety-nine dietitians completed the survey. Most participants recommended one to two different medical nutrition therapy strategies for preoperative weight loss (n = 69, 74%), with a very-low-energy diet exclusively from liquid meal replacements being the most frequently prescribed (n = 62, 69%). A significantly higher proportion of dietitians working privately reported the involvement of a bariatric surgeon in the multidisciplinary team (P = 0.002). More private practitioners also reported providing education on the nutritional consequences of the different types of bariatric procedures (P = 0.005) and postoperative vitamin and mineral supplementation (P = 0.013), as well as the use of the guidelines to guide their practice (P = 0.014), compared to dietitians who worked in the public sector. A higher proportion of dietitians working in metropolitan areas reported that screening occurred more frequently for vitamin D (P = 0.008), fasting blood lipids (P = 0.03) and glycated haemoglobin (P = 0.003) compared to those in regional/rural/remote areas.

CONCLUSIONS

Reported preoperative screening practices were not consistent with the recommendations from the literature and current American guidelines. Further investigation into the difference in the nutritional management strategies and work environments is warranted.

Effects of short-term energy restriction on liver lipid content and inflammatory status in severely obese adults: Results of a randomized controlled trial using 2 dietary approaches

Short-term very-low-energy diets (VLEDs) are used in clinical practice prior to bariatric surgery, but regimens vary and outcomes of a short intervention are unclear. We examined the effect of 2 VLEDs, a food-based diet (FD) and a meal-replacement plan (MRP; LighterLife UK Limited, Harlow, UK), over the course of 2 weeks in a randomized controlled trial. We collected clinical and anthropometric data, fasting blood samples, and dietary evaluation questionnaires. Surgeons took liver biopsies and made a visual assessment of the liver. We enrolled 60 participants of whom 54 completed the study (FD, n = 26; MRP, n = 28). Baseline demographic features, reported energy intake, dietary evaluation and liver histology were similar in the 2 groups. Both diets induced significant weight loss. Perceived difficulty of surgery correlated significantly with the degree of steatosis on histology. There were reductions in the circulating inflammatory mediators C-reactive protein, fetuin-A and interleukin-6 between baseline (pre-diet) and post-diet. The diets achieved similar weight loss and reduction in inflammatory biomarkers. There were no significant differences in perceived operative difficulty or between patients' evaluation of diet satisfaction, ease of use or hunger frequency. Non-alcoholic fatty liver disease histology assessments post-diet were also not significantly different between diets. The results of this study show the effectiveness of short-term VLEDs and energy restriction, irrespective of macronutrient composition, although the small sample size precluded detection of subtle differences between interventions.

Age increases MCP-1 level in association with bariatric surgery operating time and metabolic risk severity

Objective

Assess the role of inflammation on operating time in younger vs. older bariatric surgery patients.

Methods

Fifty‐five younger (F: 46, Age: 34.9 ± 4.0 years, body mass index [BMI]: 48.2 ± 1.0 kg m⁻²) and 48 older (F: 34, Age: 57.0 ± 5.1 years, BMI: 46.8 ± 1.0 kg m⁻²) adults were studied prior to surgery. Blood pressure, glycaemic control (fasting glucose/insulin, HbA_1c), lipids (high‐density lipoprotein and triglycerides) and inflammation (monocyte chemoattractant protein‐1 [MCP‐1]) were assessed. Metabolic risk severity z‐scores were calculated from clinical outcomes. Omental adipose biopsies were collected at surgery for MCP‐1 protein analysis. Operating time was used to characterize surgical difficulty.

Results

Older vs. younger adults had higher HbA_1c (P = 0.03). There was no difference in BMI, lipids, metabolic risk severity or insulin between groups, but operating time was longer in older vs. younger individuals (P = 0.04). Circulating MCP‐1 was also elevated in older vs. younger adults (P = 0.04) independent of HbA_1c, although this was not explained by omental fat. Nevertheless, serum MCP‐1 was associated with increased metabolic risk severity (R = 0.27, P = 0.01). In addition, operating time was linked to HbA_1c (R = 0.30, P = 0.01) and omental MCP‐1 protein (R = 0.31, P < 0.01).

Conclusions

MCP‐1 is associated with longer operating time and increased metabolic risk severity in older bariatric patients independent of glycaemic control. Pre‐operative treatment of inflammation may be required to enhance surgery effectiveness.

Nutrition and metabolic support recommendations for the bariatric patient

Managing the metabolic needs of the patient with obesity is a challenge unto itself without the added demands of accounting for an altered gastrointestinal tract. Nevertheless, with about 200,000 bariatric procedures being performed annually in the United States, clinicians must be prepared to manage the critically ill bariatric surgery patient. This article reviews the recent literature relating to nutrient needs and metabolic support for the bariatric patient. Bariatric patients are at risk for several micronutrient deficiencies, including vitamins D and B₁₂, calcium, and iron; some bariatric procedures affect macronutrient needs as well. Literature on nutrition support guidelines for the bariatric population is limited. However, with an understanding of the anatomical and physiological effects of bariatric surgery, recent guidelines for critically ill patients with obesity can be applied to the bariatric surgery population. The unique needs of the bariatric population, such as susceptibility to micronutrient deficiencies and specialized access routes, must be considered to provide safe and efficacious nutrition support. Further research is necessary to develop specific nutrition support recommendations for the bariatric population.

Water with food intake does not influence caloric intake after gastric bypass (GBP): a cross-over trial

BACKGROUND

Bariatric patients seeking information meet very different recommendations on postoperative diet and eating behaviour. A reason for variability may be lack of hard evidence. A national survey on current dietary advice was conducted to serve as background for the present study on how drinking during a meal influenced caloric consumption.

METHODS

A standardised questionnaire was sent to all units in the Scandinavian Obesity surgery registry (SOReg) in order to obtain information regarding current diet advice after gastric bypass. Twenty-eight patients, 14 in each group, were studied either 2 months or 1 year after a standard gastric bypass (GBP). A standardised lunch was served on two separate days with or without water in randomised order. Meal and water weights were measured before and after. Hunger/satiety scores were obtained using visual analogue scales.

RESULTS

Response rate for surgeons was low, for dieticians 75 %. No clear consensus for liquid intake during meals was found; few surgeons advised patients whether or not to drink with meals. All patients ate to full satiety. Two months post-GBP, 7/14 patients consumed more solid food when allowed drinking water; the increase in caloric consumption was not significant. One year post-GBP, 5/14 patients consumed more solid food when allowed drinking water, the difference not reaching statistical significance.

CONCLUSION

Our study does not indicate that patients should refrain from drinking during meals the first year after a GBP, at least not from a caloric intake point of view.