Embarking on the journey toward weight loss surgery is a significant step toward achieving your health and wellness goals. Before undergoing the procedure, it’s essential to prepare your body and mind for the transformative journey ahead. This article provides insights, tips, and reassurance to support you on your path toward a healthier future, focusing on the specifics of the pre-operative diet.
Bariatric surgery (BS) is today the most effective therapy for inducing long-term weight loss and for reducing comorbidity burden and mortality in patients with severe obesity. On the other hand, BS may be associated to new clinical problems, complications and side effects, in particular in the nutritional domain. Therefore, the nutritional management of the bariatric patients requires specific nutritional skills. In this paper, a brief overview of the nutritional management of the bariatric patients will be provided from pre-operative to post-operative phase.
Goals and Expectations
During the 6-month diet before weight loss surgery, the primary goal is not only to lose weight but also to improve overall health and readiness for the procedure. While weight loss goals may vary depending on individual factors such as starting weight and medical history, aiming to lose 5-10% of your body weight is generally considered realistic and achievable. Preoperative weight loss before BS is still a matter of debate. At present, most relevant guidelines do not provide any clear indication about pre-operative weight loss.
Your bariatric surgeon and registered dietitian will work closely with you to establish personalized weight loss goals based on your specific needs and circumstances. The 6-month diet before weight loss surgery serves as a foundation for long-term weight management and success post-surgery.
Diet Strictness and Guidelines
The strictness of the 6-month diet before weight loss surgery may vary depending on your bariatric surgeon’s recommendations and your individual health needs. However, it’s essential to adhere closely to the guidelines provided by your bariatric surgery team to maximize the benefits of the pre-operative diet.
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The pre-surgery diet focuses on preparing your body for surgery by reducing liver size, promoting weight loss, and optimizing health. The reason behind this is that your liver sits on top of your stomach where the surgeon will be working. So if the size of the liver is too large, it can make it difficult to see your stomach and perform the necessary tasks during the surgery.
Gradually transitioning to solid foods that are easy to digest, focusing on lean protein, fruits, vegetables, and whole grains. Regardless of the diet phase, portion control and nutrient density are key principles to emphasize. Eating smaller meals more frequently throughout the day can help regulate blood sugar levels and keep hunger at bay.
The pre-operative diet typically includes lean sources of protein like fish, poultry, and eggs, as well as complex carbohydrates such as whole grains and legumes. Fruits and vegetables in their natural state are always encouraged. It is also important to drink plenty of water throughout the day to stay hydrated - at least eight 8 oz glasses daily - while avoiding sugary drinks like soda and juice. It’s essential to stay well-hydrated before surgery by consuming at least 92 ounces of fluids per day, including water, herbal tea, and sugar-free beverages.
While occasional indulgences may be permissible at the start, it’s essential to stick to the pre-operative diet plan to make the most of the benefits and improve surgical outcomes. Alcohol consumption is typically discouraged during the 6-month diet before weight loss surgery.
The Importance of Nutritional Assessment
Assessment of nutritional status of candidates to BS before the operation plays an important role in the post-surgical management. During the last few years, several studies demonstrated that patients with severe obesity often display micronutrient deficiencies (MDs) when compared to normal weight controls.
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In 2008, Asheim et al. analyzed the vitamin status of 110 patients affected by severe obesity as compared with 58 normal weight subjects: patients with obesity had significantly lower concentrations of vitamins A, B6, C, 25-hydroxyvitamin D, and lipid-standardized vitamin E [4]. Similarly, Van Rutte et al. demonstrated in 200 patients affected by severe obesity that 38% of them had low serum iron, 24% had low serum folate, 11% had low serum vit. B12 and 81% had hypovitaminosis D (55% severe deficiency with a level < 30 nmol/l) [5]. Finally, Peterson et al. MDs in patients with severe obesity could be attributed to a poor-quality, non-varied, high-calorie and high-fat diet. For example, excessive simple sugar, milk products or fats could lead to a deficit of vitamin B1 [7]. Moreover, iron status could be affected by adipose tissue inflammation and increased expression of the systemic iron regulatory protein hepcidin [8]. Assessment and correction of the nutritional status before the procedure in BS candidates is considered important for the prevention of post-bariatric MDs (see below). Indeed, Schiavo et al.
Patients with severe obesity often display micronutrient deficiencies when compared to normal weight controls. Therefore, nutritional status should be checked in every patient and correction of deficiencies attempted before surgery.
The Role of Physical Activity
While dietary modifications are a central focus of the 6-month diet before weight loss surgery, incorporating regular physical activity is also encouraged to support weight loss and overall health. Before starting any exercise program, it’s essential to consult with your primary physician to ensure that it is safe and appropriate for your individual needs and medical history.
In addition to dietary changes, it is often recommended that those embarking on this six-month diet plan increase their physical activity levels by doing 30 minutes or more of aerobic exercise at least three times per week. In addition to following a healthy diet, it is important to implement regular physical activity into your routine. Your doctor may suggest light exercises such as walking or jogging, swimming, yoga, and Pilates.
Preoperative Weight Loss: Evidence and Methods
At present, evidences from randomized and retrospective studies do not support the hypothesis that pre-operative weight loss could improve weight loss after BS surgery, and the insurance-mandated policy of a preoperative weight loss as a pre-requisite for admission to surgery is not supported by medical evidence. The lack of clear indications for preoperative weight loss is probably related to the low evidence available on this topic.
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On the contrary, some studies suggest that a modest weight loss of 5-10% in the immediate preoperative period could facilitate surgery and reduce the risk of complications. A modest weight loss of 5-10% in the immediate preoperative period has been suggested as a mean to facilitate surgery and reduce the risk of complications.
Very low calories diet (VLCD) and very low calories ketogenic diets (VLCKD) are the most frequently used methods for the induction of a pre-operative weight loss today. Preoperative weight loss can be obtained with several regimens, such as low-calorie diets (LCD) (800-1200 kcal/day), very low-calorie diets (VLCD) (600 kcal/day), or a hypocaloric diet combined with IGB placement, and the question of which method provides the best results in terms of weight loss and patients’ compliance, tolerance, and acceptance is still under debate. A pre-operative VLCD may also induce a significant weight loss before BS, being faster, cheaper, and with fewer side effects than IGB [31].
Studies on Preoperative Weight Loss
We decided to perform a systematic analysis and we searched all articles identified as clinical trials and published in the last 10 years in PubMed with the terms “preoperative weight loss and obesity and/or bariatric surgery”. The search was conducted between June 1, 2019 and July 31, 2019 and all articles available in English were included. A total of 243 articles were retrieved: 111 duplicate articles were eliminated and further 84 were excluded because not related to the topic. Abstracts from the remaining articles where evaluated, leaving 25 full articles concerning weight loss prior surgery. After reading the full text, we concluded that only 7 out of 25 papers focused on the effects of weight loss prior to BS [13-19], and only 3 of them were randomized control trials specifically comparing patients who achieved a significant weight loss before surgery with patients who did not [13-15]. The characteristics of the three trials are reported in Table 1. Main aims of the trials were to assess if weight loss before surgery may improve the operating time [13, 15], the intra-operative complications rate [13], the surgeons perceived difficulty [13], the 30 days post-operative complications [13, 14], and the post-operative weight loss [14, 15]. The three studies presented a large heterogeneity concerning the way in which weight loss was achieved: Van Nieuwenhove et al. compared patients randomly allocated to a 2-week preoperative VLCD regimen or no preoperative dietary restriction [13], Kalarchian et al. compared patients receiving a 6-month behavioral lifestyle intervention to usual pre-surgical care [14], and Coffin et al. evaluated the impact of an intra-gastric balloon (IGB) [15]. Higher in control group vs. Higher in control group vs.
Retrospective Studies
Apart from the few randomized trials included in our meta-analysis, most of the works on the effects of weight loss prior BS on post-surgery weight loss are retrospective studies. Giordano & Victorzon compared patients who achieved different amount of pre-operative weight loss (< 5%, > 5 to 10% and > 10%) in a retrospective study with a total sample of 548 patients: post-operative weight loss was higher in patients who achieved > 10% weight loss at 12 months, with no significant differences observed at 24 months [16]. Sherman WE et al. analyzed a cohort of 141 patients treated with sleeve gastrectomy (SG) and demonstrated that the percentage of excess BMI loss 1 year after SG was not statistically different between those who lost weight and those who gained weight before surgery [20]. McNickle & Bonomo did not found any association between pre-operative weight loss and 1-year outcomes in a cohort of 127 patients treated with a standardized 6-month medical weight loss program and a 2-week pre-operative diet with meal replacements before SG [21]. Moreover, the analysis of the data derived from the insurance mandated medical programs before BS conclude there is no evidence of any kind that insurance-mandated preoperative weight loss has any clear impact on postoperative outcomes or weight loss.
Benefits of Preoperative Weight Loss
Although BS has a low mortality rate, surgical complications (e.g., anastomotic leakage, bleeding, and infections) remain common (5-20%) and partly dependent on patient factors like age, sex, and comorbidity [23]. Laparoscopic surgery in patients with severe obesity is challenging because of the thickness of the abdominal wall, intra-abdominal obesity, possible mesenteric thickening, and hepatomegaly [24]. The presence of visceral fat can increase the complexity and risk in patients undergoing any type of abdominal surgery [25]. Thickened abdominal walls may limit precise surgical movements during laparoscopy, and intra-abdominal obesity can limit visibility during surgical procedures.
Nonalcoholic fatty liver disease (NAFLD) is a condition frequently complicating obesity that can lead to an increase in liver fat infiltration, mainly in the left lobe, making the liver brittle and more susceptible to injury and bleeding. During laparoscopic bariatric surgery, hepatomegaly and visceral fat in the left upper quadrant may limit preliminary exposure of the surgical field [26-28] and may increase the conversion rate and operative time [29]. Preoperative weight loss by means of a VLCD has been reported to reduce liver size and intra-abdominal fat mass, blood loss, short-term complications as well as operation time and length of hospital stay [13, 26, 27, 32, 33].
VLCD vs. LCD
Andrianzen Vargas et al. showed that LCD is insufficient in 60% of cases to achieve the intended 10% weight loss, while VLCD is able to achieve it in practically all patients [31]. However, a systematic review confirmed that VLCD led to a significant weight loss (− 2.8 to − 14.8 kg) and liver size reduction (5-20% of the initial volume), but did not found a reduction in peri-operative complications [34]. However, a more recent study comparing the effect of VLCD and LCD before surgery showed that, although VLCD was more effective in reducing total body weight (5.8 vs.
Very Low-Calorie Ketogenic Diet (VLCKD)
More recently, very low-calorie ketogenic diet (VLCKD) has been proposed as a new effective and safe method for achieving effective preoperative weight loss. Previous studies reported that VLCKDs are effective for weight loss and safe in non-surgical contexts [36]. On the other hand, it must be considered that any very low-calorie regimen drives a catabolic state and an increased oxidative stress that may have a negative impact on surgical outcomes. In addition, the ketogenic diet, based only on a protein substrate, may induce an adaptive response in several organs, with physiological modifications potentially unsafe in the perioperative period.
Studies on VLCKD
To date only few studies addressed the role of VLCKD immediately before BS, and the available data are actually scarce. Leonetti et al. evaluated in an uncontrolled study the compliance, safety, and effectiveness of a sequential regimen (VLCKD for 10 days, followed by a VLCD for 10 days, and then a LCD for 10 days) in patients with obesity scheduled for BS. The study showed an adequate short-term reduction of body weight and waist circumference, without dangerous alteration in renal, hepatic, and metabolic functions. The weight loss was similar to that obtained with a VLCD and better than reported for LCD [37]. A similar 30-day sequential preoperative regimen was used in another uncontrolled study showing a significant reduction in weight, waist circumference and visceral fat, and an improvement in several clinical parameters, including glycemic and lipid profiles. Moreover, a mean 30% reduction in liver volume was also observed [38]. Finally, in a third non randomized study, patients were treated with either VLCKD or VLCD for 3 weeks prior to BS. Weight loss was not significantly better in the VLCKD than in the VLCD group, but VLCKD had better results on surgical outcomes, influencing drainage output, post-operative hemoglobin levels, and hospital stay.
Conclusion on Preoperative Weight Loss Methods
In conclusion, there is a general agreement on the beneficial effects of a modest weight loss in the immediate pre-surgical period on the surgical and anesthesiological risks. Efficacy of VLCD regimens and IGB as bridging therapy before BS is consolidated in literature, while the role of VLCKD is arising in importance, but still under debate in the pre-operative period.
Insurance Considerations and Medical Weight Management (MWM) Programs
Although weight loss surgery is gaining recognition as a preventive measure for your health, there are some steps many patients need to take for coverage. In many cases, this 6-month diet before weight loss surgery is one of the requirements.
Many insurance companies require a set period of MWM (typically 4-6 months) as prerequisite for approval for bariatric surgery. The justification is presumably to enhance postoperative weight loss outcomes and ensure dietary compliance.
Studies on MWM
A retrospective review of all patients undergoing bariatric surgery at our institution between 2009 and 2013 was conducted. Institutional Review Board approval was obtained. All patients met the 1991 NIH consensus criteria for bariatric surgery [4]. Patients were stratified by payor mix on the basis of whether the insurance company required any MWM. Because there were inherent differences between the 2 groups, a bucket matching algorithm was applied to match 1 MWM patient to 3 controls to create the final cohort. Patients were matched based on gender, age, body mass index (BMI), and surgical procedure. A repeated-measures model was then generated to compare the estimated differences in percent excess weight loss (%EWL), percent excess body mass index loss, and percent total weight loss at 12 and 24 months. For men, ideal body weight (IBW) was calculated as IBW = 51.65kg þ 1.85 kg/inch of height greater than 5 feet. For women, IBW = 48.67 kg þ 1.65 kg/ inch of height greater than 5 feet [5]. An ideal BMI of 25 was assumed for all patients.
A total of 1432 bariatric surgery patients were reviewed for analysis. Demographic characteristics are shown in Table 1. Most patients (89%) were covered by insurance that did not require MWM. The bucket-matching algorithm resulted in a total sample size of 560 patients (140 MWM patients and 420 controls), consisting of gastric bands (41%), sleeve gastrectomies (40%), and gastric bypasses (19%). The demographic characteristics of the matched cohort are listed in Table 3. The matched groups were used to evaluate differences in % EWL, percent excess body mass index loss, and percent total weight loss at 1 and 2 years postsurgery. The repeated-measures model found no difference in weight loss out-comes between the 2 groups at 1 and 2 years (Table 4 and Fig.
Conclusion on MWM
This study adds to the existing literature regarding the overall lack of benefit for insurance-mandated MWM. In 2006, Jamal et al. retrospectively compared 72 gastric bypass patients who underwent mandatory MWM (13 weeks) to 252 patients who did not [3]. At 1 year follow-up, the non-MWM patients had higher %EWL (67% versus 60%, p <.0001). The MWM group had a higher dropout rate (28% versus 19%, p <.05). They concluded that insurance-mandated MWM programs have no benefit and may be an obstacle to patient access for bariatric surgery. In 2010, Ochner, Puma, Raevuori, Teixeira, and Geliebter compared 94 gastric bypass patients who underwent mandatory MWM (6 months) with 59 patients who did not [2]. They found that the 6-month MWM requirement was ineffective in reducing weight before surgery. Finally, we performed a small randomized study in 2008 of 55 patients who were randomized to 6 months of MWM versus usual care [6]. There is some data suggesting preoperative weight loss leads to improved clinical outcomes and less postoperative complications, particularly in the super-obese.
There was no difference in weight loss outcomes up to 2 years in patients who required insurance-mandated MWM programs.
Post-Operative Diet
While a pre-op diet is designed to prepare you for procedures such as a gastric sleeve or gastric bypass surgery, the post-op diet is designed to help your body heal and adapt to the sudden changes in your digestive system.
In the following two weeks after surgery, the diet program consists of a liquid-only diet, which can include protein drinks, sugar-free/caffeine-free drinks, and of course lots of water. Eventually, you’ll move on to solid foods and meals that will make up the bulk of your diet going forward.
After surgery, nutritional counselling is recommended in order to facilitate the adaptation of the eating habits to the new gastro-intestinal physiology. Nutritional deficits may arise according to the type of bariatric procedure and they should be prevented, diagnosed and eventually treated. Finally, specific nutritional problems, like dumping syndrome and reactive hypoglycaemia, can occur and should be managed largely by nutritional manipulation.
After the procedure, nutritional counselling is important in order to facilitate the adaptation of the eating habits to the new gastro-intestinal physiology. Nutritional deficits may arise according to the type of bariatric procedure and they should be prevented and eventually treated. Finally, specific nutritional problems, like dumping syndrome and reactive hypoglycaemia, can occur and should be managed largely by nutritional manipulation.
Step 2 also lasts one to two weeks and includes blended or pureed food that is high in protein and low in fat (no vegetables). Also, even though the liquid diet step is over, it’s still important for you to maintain the commitment to drink 64 ounces of fluids per day to avoid dehydration (about 4 to 6 ounces of liquid every hour). Step 3 lasts up to three months. During this phase, you are able to eat the same foods as Step 2 but without the need for them to be blended or pureed. About three to four months after bariatric surgery, you are ready to begin the diet you should follow the rest of your life. “It’s important to eat protein at every meal and eat the majority of it first so you can meet your protein goals,” Lisa said. The “30-minute rule”: After surgery, you have a smaller stomach, so you should not drink any liquids for 30 minutes before a meal, during the meal, and for 30 minutes after a meal. Not drinking prevents you from feeling full too quickly before you’ve finished eating your protein.