Bariatric surgery is often considered the most effective treatment for severe obesity, promoting long-term weight loss and reducing obesity-related comorbidities. However, the success and safety of bariatric surgery can be affected by factors such as increased abdominal wall thickness, increased visceral adiposity, and the presence of an enlarged liver. Up to 90% of candidates for bariatric surgery have nonalcoholic fatty liver disease (NAFLD), characterized by an enlarged and fatty liver.
To mitigate these risks, an energy-restricted diet is often prescribed before bariatric surgery to reduce weight and liver volume. This pre-operative diet, often called the "liver shrinking diet" or "liver reduction diet," aims to make the surgery safer and more manageable. This article delves into the liver shrinking diet, its benefits, potential side effects, and what you can expect before undergoing bariatric surgery.
What is a Liver-Shrinking Diet?
The liver-shrinking diet is a specialized eating plan that patients follow for a few weeks before bariatric surgery. It differs significantly from typical diets, focusing on significantly reducing caloric and carbohydrate intake. While bariatric weight loss centers usually provide specific diet plans and menus tailored to each patient, the primary goal remains the same: to facilitate weight loss and reduce liver size before surgery.
Why is a Liver-Shrinking Diet Necessary?
Obesity often leads to unhealthy eating habits high in fat, salt, and sugar, contributing to an enlarged liver. While alcoholism is often associated with fatty liver disease, obesity is the leading cause. An enlarged liver can pose challenges during bariatric surgery because the liver sits directly on top of the stomach when a patient is lying down. Surgeons need access to the stomach to perform the operation, and an enlarged liver can obstruct their view and maneuverability, increasing the risk of complications. Thus, the pre-surgery diet is designed to shrink the liver, aiding the surgeon and ensuring patient safety.
How Long Do You Need to Follow the Liver-Shrinking Diet?
The duration of the liver reduction diet is determined by the bariatric surgeon, often based on the patient's starting BMI (Body Mass Index). Here is a general guideline:
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- BMI 35-39.9: 1 Week
- BMI 40-49.9: 2 Weeks
- BMI 50-59.9: 3 Weeks
In general, the pre bariatric surgery diet will last no more than 4 weeks.
How Does the Liver-Shrinking Diet Work?
The liver-shrinking diet works by targeting glycogen stores in the liver. Carbohydrates provide energy in the form of glycogen, which is stored in the liver and muscles. When carbohydrate consumption is high, the body stores more glycogen, and glycogen binds with water (every gram of glycogen stores 3 grams of water). This leads to liver enlargement.
The liver-shrinking diet is high in protein and low in fat and carbohydrates. This forces the body to use stored glycogen, reducing water retention and shrinking the liver. Patients with higher BMIs may require a longer duration on the diet for optimal liver reduction.
What Can You Eat During the Liver-Shrinking Diet?
Bariatric surgeons provide a specific diet plan and a list of approved foods. The two main plans are:
Protein Shake-Based Plan: This plan primarily consists of protein shakes with one solid meal per day. It may be suitable for individuals with busy schedules who prefer not to cook or prepare food.
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Diverse Meal Plan: This plan offers more variety but requires meal preparation. Some patients alternate between the two plans.
Liver-Shrinking Diet Protein Shake Criteria:
- No more than 200 calories.
- 20-25 grams of protein.
- 15 grams or less of carbohydrates.
- 5 grams or less of sugar.
- Less than 10% of the daily recommended amount of total fat.
Powdered supplements can be mixed with unsweetened almond milk, unsweetened soy milk, 1% milk, or water. Avoid adding extras like fruit or avocado.
Sample Liver-Shrinking Diet:
- Breakfast: Protein shake.
- Lunch: Lean protein (e.g., grilled chicken or fish) with non-starchy vegetables (e.g., broccoli or spinach).
- Dinner: Protein shake or a small portion of lean protein with non-starchy vegetables.
- Snacks: Small portions of approved fruits or vegetables.
Drink at least 64 ounces of water and other approved beverages daily.
Can You Drink Coffee on the Liver-Shrinking Diet?
Yes, black coffee (usually decaffeinated) is typically allowed. However, avoid adding creamer or sugar, as this can increase carbohydrate and fat intake.
What Happens if You Cheat on the Liver-Shrinking Diet?
Cheating on the liver-shrinking diet can compromise your safety and may lead to the rescheduling of your surgery. If the liver does not reduce adequately, the surgeon may not be able to perform the surgery safely. It is essential to adhere strictly to the diet plan provided by your bariatric surgeon.
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How Much Weight Can You Lose?
Most patients lose between 5 to 15 pounds on the pre-bariatric surgery liver shrinking diet.
How Can You Tell if Your Liver is Shrinking?
Without a CT scan, it's difficult to determine if your liver has decreased in size. However, weight loss while following the liver-shrinking diet is a good indication that the diet is working.
Low-Calorie Diets (LCDs) and Liver Volume Reduction
A systematic review of studies has explored the effectiveness of low-calorie diets (LCDs, 800-1500 kcal per day) on liver volume reduction in patients awaiting bariatric surgery. The review included eight studies with a total of 251 patients, examining nine different diets ranging from 800 to 1200 kcal, lasting between 2 to 8 weeks.
The results indicated that LCDs are effective in reducing liver volume (12-27%) and promoting weight loss (4-17%), particularly in the initial weeks. Patients generally showed acceptable compliance with LCDs.
Comparing LCDs to Very-Low-Calorie Diets (VLCDs)
Very-low-calorie diets (VLCDs, 450-800 kcal per day) have also been shown to effectively reduce liver volume. A 2017 systematic review indicated that VLCDs could reduce liver volume by 5-20% (mean 14%). However, VLCDs carry potential risks, including the loss of lean body mass (LBM) and symptoms like fatigue, headache, and nausea, which can affect compliance.
LCDs appear to offer a balance between effectiveness and tolerability. While VLCDs may lead to a slightly greater reduction in liver volume, LCDs are associated with less LBM loss and fewer side effects. One study found that 51% of the weight loss on an LCD was attributed to LBM loss, compared to 62% with a VLCD.
Potential Risks and Side Effects of Liver-Shrinking Diets
When prescribing a VLCD and LCD, there are potential risks that need to be considered. One of the two prevailing risks is that the diet may turn the body into a catabolic state leading to lean body mass (LBM) loss. A decreased LBM could negatively impact energy balance, functional capacity and cardiovascular health, which may impede recovery after bariatric surgery. Secondly, the patient may experience symptoms related to the catabolic state like fatigue, headache and nausea compromising the compliance and acceptability of the diet. How these risks relate to the level of dietary restriction is unclear, but it is intuitive that the risks are larger in a higher degree of caloric restriction.
Benefits of Liver Shrinking Diets
Reduced Surgical Complexity
Some studies suggest that following an LCD can improve surgical complexity, while others report no change. However, there is evidence that surgical duration may decrease with pre-operative LCDs.
Reduced Post-Operative Complications
Weight loss achieved through a liver-shrinking diet can reduce the risk of post-operative complications. A Scandinavian study involving over 22,000 patients found that a weight loss of approximately 5% reduced the risk of overall postoperative complications by 13-18%.
Improved Tolerance and Compliance
LCDs are generally well-tolerated, with high compliance rates (80-89%). However, some studies use subjective methods to determine compliance, such as counting returned empty formula sachets and interviewing patients without blinding.
Tips for Sticking to the Liver-Shrinking Diet
- Choose the Right Protein Shake: Opt for shakes that meet the specified criteria for calories, protein, carbohydrates, sugar, and fat.
- Stay Hydrated: Drink at least 64 ounces of sugar-free, calorie-free beverages per day.
- Eat All Your Portions: Due to the restrictive nature of the diet, ensure you consume all the portions allocated throughout the day.
- Prepare Ahead of Time: Plan and prepare your meals in advance to make it easier to adhere to the diet.
The Importance of a Multidisciplinary Approach
A personalized approach to pre-operative diets, guided by a multidisciplinary team, may be more beneficial than a universal LCD. Different patients with varying BMIs and comorbidities may have different goals, such as reducing liver volume or stabilizing glucose levels.