Metabolic/bariatric surgery (MBS) stands as the most effective intervention for individuals grappling with morbid obesity and its associated comorbidities, such as type 2 diabetes. Its efficacy extends beyond short-term weight reduction, demonstrating the ability to sustain lower body weights for extended periods, thereby enhancing the patient's quality of life and prolonging their life expectancy. For patients contemplating bariatric surgery, understanding the potential outcomes is paramount, enabling them to make well-informed decisions. Similarly, healthcare providers rely on these outcomes to gauge the patient's progress post-surgery and administer timely interventions when necessary. Several clinical factors influence weight loss after MBS, including the patient's initial body mass index (BMI), age, gender, ethnicity, and the specific surgical procedure employed. A reliable weight loss prediction model can significantly aid patient counseling and goal setting.
The Growing Prevalence of Obesity
Globally, obesity rates have been steadily climbing. According to the 2019 Organisation for Economic Co-operation and Development health statistics, the prevalence of obesity, defined as a BMI exceeding 30 kg/m2, rose from 21% in 2010 to 24% in 2016 among adults over 30 years of age. Projections indicate a continued upward trajectory by 2030. Obesity and its related health complications are anticipated to reduce life expectancy by 0.9 to 4.2 years, depending on the country. While the prevalence of individuals with a BMI >30 kg/m2 was reported as 5.2% in Korea in 2018, this figure is lower than in many other countries. However, considering physiological differences, a BMI ≥25 kg/m2 is considered a more appropriate definition of obesity for the Asian population. Using this standard, the proportion of obese individuals in Korea in 2018 was approximately 38.5%, comparable to that in the Western world. Notably, the prevalence of obesity across all classes has been increasing in Korea over the past decade, with class III obesity (BMI above 35 kg/m2 for Asians) nearly tripling, reaching over 0.8% in 2018. This increase is particularly rapid among individuals under 40 years of age, with class III obesity reaching 1.6% in this age group, three or more times higher than in older generations.
The Efficacy of Metabolic and Bariatric Surgery
MBS is widely recognized as the most effective treatment for morbid obesity and related comorbidities. Clinical trials have consistently demonstrated that surgical interventions yield superior weight loss outcomes compared to medical management. Furthermore, MBS leads to better resolution or improvement of obesity-related comorbidities such as type 2 diabetes, dyslipidemia, and hypertension. The benefits of MBS extend beyond short-term weight loss, as it has been shown to maintain lower body weights for several decades, thereby enhancing the patient's quality of life and prolonging life expectancy. In light of these benefits, the Korean National Health Insurance plan began covering MBS in 2019, making it accessible to patients with a BMI above 35 kg/m2 or a BMI above 30 kg/m2 with obesity-related comorbidities.
Understanding Weight Loss Reporting Systems
To interpret the literature on weight loss after MBS, it is crucial to understand the commonly used weight loss reporting systems. The percentage of excess weight loss (%EWL) is calculated based on the excess weight beyond the ideal body weight. Initially, the ideal body weight was derived from a Metropolitan Life Insurance Company table released in 1983. However, in 2005, bariatric societies recommended using a BMI of 25 kg/m2 as the criterion for calculating weight loss. Traditionally, surgeons have reported weight loss outcomes as %EWL or %EBMIL (percentage of excess BMI loss) and change in BMI. Nevertheless, some have argued that the %EWL or %EBMIL metric should be abandoned. Studies have shown that absolute BMI values and %EWL results are significantly influenced by initial BMI, unlike the percentage of total weight loss (%TWL). This means that individuals with super-obesity may find it challenging to reach a target BMI of 35 kg/m2 due to the larger amount of weight they need to lose compared to those with less obesity.
Patient Expectations vs. Clinical Reality
Bariatric surgery candidates often have weight loss expectations that exceed clinically reasonable outcomes. A study of sleeve gastrectomy (SG) candidates revealed that almost all participants believed they would achieve their desired, satisfactory, or at least acceptable weight loss expectations within one year after surgery. However, these expectations were significantly higher than the clinically expected %EWL. Weight loss outcomes vary considerably among patients, even when using the %TWL metric, which is least influenced by baseline BMI. A retrospective study of Roux-en-Y gastric bypass (RYGB) and SG patients showed that most patients reached their maximal weight loss between 12 and 18 months after surgery, with RYGB demonstrating slightly better weight loss. Nonetheless, the maximal %TWL exhibited wide variability, ranging from less than 5% to 60% for both procedures. Understanding the factors that contribute to weight loss differences among bariatric patients is essential for setting realistic weight loss goals for individual patients.
Read also: Comprehensive Guide to Gastric Bypass Diet
Factors Influencing Weight Loss Outcomes
Several factors can influence weight loss outcomes after MBS.
Preoperative BMI
Preoperative BMI has a significant impact on weight loss outcomes. Research has demonstrated a clear correlation between initial BMI before surgery and final BMI after surgery. Patients with higher initial BMIs tend to have higher BMIs even after substantial weight loss. A study reported that baseline BMI had the largest impact on weight nadir after RYGB among 12 preoperative variables.
Age
Age at the time of surgery also affects weight loss outcomes. Studies have shown that older patients tend to experience less weight loss and a greater tendency for weight regain in the long term.
Gender
Gender is another clinical factor that may influence weight loss outcomes. Some studies suggest that women tend to experience greater weight loss after MBS, while others indicate that being a woman may be an unfavorable predictor of weight loss.
Ethnicity
The effects of ethnicity on postoperative weight loss have been a subject of ongoing discussion. Studies have revealed differences in weight loss outcomes based on ethnicity. For instance, weight loss after RYGB has been found to be highest in Caucasians and lowest in non-Hispanic Black patients. Differences in weight loss outcomes after MBS have also been observed among Asian ethnicities.
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Type 2 Diabetes
Type 2 diabetes is a prognostic factor for poorer weight loss after MBS. Studies have shown that diabetes is independently associated with poor weight loss, particularly in those using insulin before surgery. Preoperative insulin use may be associated with weight gain, potentially hindering weight loss after MBS.
Mental Health Conditions
Mental health conditions, especially those related to eating behaviors, may also be a preoperative predictor of weight loss after MBS. A significant proportion of MBS candidates report having mental illnesses, with depression and binge eating disorder being the most common. The association between preoperative mental health conditions and postoperative weight loss has been inconsistent in the literature.
Type of Surgery
The type of surgery plays a crucial role in weight loss outcomes. While SG and RYGB may produce comparable weight loss in the early postoperative period, the difference tends to increase over time, favoring RYGB in terms of sustained weight loss.
Weight Loss Prediction Models
Efforts have been made to develop tools for predicting weight loss outcomes after MBS. However, most existing models are derived from single-center data and predict static weight loss outcomes at a specific time point, such as at one year, or the nadir weight. These models do not provide information about whether a patient's weight loss trajectory is on track in the early postoperative period. Research suggests that the success of MBS can be predicted as early as 3 to 6 months after surgery. Early postoperative weight changes have been shown to predict weight loss at 12 months after RYGB. Therefore, monitoring chronological weight changes in the early postoperative period is important. Recently, more comprehensive and intuitive weight loss calculators have been released, utilizing numerous clinical variables to provide personalized outcomes regarding expected weight loss and the resolution rate of comorbidities.
Dietary Guidelines After Gastric Bypass Surgery
Following gastric bypass surgery, adhering to a specific diet is crucial for recovery and achieving weight loss goals. A staged approach is typically recommended to gradually reintroduce solid foods.
Read also: Guide to Pureed Foods Post-Surgery
Stage 1: Clear Liquids
For the first day or so after surgery, only clear liquids are allowed.
Stage 2: Pureed Foods
After about a week of tolerating liquids, strained, blended, or mashed-up foods can be introduced. Meals should be small, consisting of 4 to 6 tablespoons of food, and consumed 3 to 6 times a day.
Stage 3: Soft Foods
After a few weeks of pureed foods, soft foods can be added to the diet with the doctor's approval. Meals should be small, consisting of one-third to one-half cup of food, and consumed 3 to 5 times a day.
Stage 4: Solid Foods
After about eight weeks, firmer foods can be gradually reintroduced. Meals should consist of 1 to 1-1/2 cups of food, consumed three times a day. The number of meals and amount of food at each meal can be adjusted based on individual tolerance.
General Dietary Recommendations
- Sip liquids between meals, not with meals.
- Eat and drink slowly, taking at least 30 minutes to eat meals and 30 to 60 minutes to drink 1 cup of liquid.
- Keep meals small and frequent.
- Chew food thoroughly.
- Focus on high-protein foods.
- Avoid foods high in fat and sugar.
- Take recommended vitamin and mineral supplements.
Potential Complications of Not Following the Diet
Failure to adhere to the recommended diet can lead to complications, including:
- Dumping syndrome: Occurs when too much food enters the small intestine quickly, causing nausea, vomiting, dizziness, sweating, and diarrhea.
- Dehydration: Can occur due to not drinking enough fluids between meals.
- Constipation.
- Blocked opening of the stomach pouch: Food can become lodged at the opening, causing nausea, vomiting, and abdominal pain.
- Weight gain or failure to lose weight.
Creating a Personalized Gastric Bypass Weight Loss Chart
A personalized gastric bypass weight loss chart can be a valuable tool for tracking progress and staying motivated. The chart should include:
- Essential information: Pre-surgery weight, height, BMI, body fat, and body measurements.
- Achievable goals: Set based on individual circumstances and surgeon's recommendations.
- Timeline: Tailored to individual goals and progress.
- Graph: To visualize progress.
Factors Affecting Gastric Bypass Weight Loss
Several factors can influence weight loss success after gastric bypass surgery:
- Dietary compliance: Adhering to a post-surgery diet plan is crucial.
- Physical activity: Regular exercise is essential for achieving and maintaining weight loss.
- Emotional and psychological factors: Addressing emotional eating and developing a healthy relationship with food is crucial.
Support and Resources for Gastric Bypass Weight Loss Success
A strong support system and access to resources are crucial for success in the gastric bypass weight loss journey.
- Bariatric support groups: Provide a community of individuals who share similar experiences.
- Professional guidance: Surgeons, dietitians, and mental health professionals can provide tailored recommendations and support.