Unlock Rapid Weight Loss with the Ultimate Bariatric Liver Shrinking Diet Guide!

Bariatric surgery stands as an effective intervention for individuals grappling with severe obesity, offering the potential for sustained weight loss and mitigation of obesity-related health issues. However, the presence of an enlarged liver, often associated with nonalcoholic fatty liver disease (NAFLD), can present technical challenges during surgery. To address this, a liver-shrinking diet is often prescribed before bariatric surgery to reduce weight and liver volume. This article delves into the guidelines surrounding bariatric liver shrinking diets, with a focus on low-calorie diets (LCDs).

The Importance of Liver Volume Reduction Before Bariatric Surgery

Bariatric surgery is considered the most effective treatment for severe obesity as it promotes long-term weight loss and reduces or controls obesity-related comorbidities. The incidence of short-term life-threatening complications is considered relatively low but depends on the patients’ comorbidities and technical difficulties that are encountered during surgery. In obese patients, technical difficulties are related to increased abdominal wall thickness, increased visceral adiposity and the presence of an enlarged liver. All these factors may contribute to reduced intra-abdominal space, reduced freedom of surgical movement and limited exposure of the gastric cardia, making the surgery technically more challenging and potentially resulting in complications. Up to 90% of candidates for bariatric surgery have nonalcoholic fatty liver disease (NAFLD) characterized by an enlarged and fatty liver. For these reasons, it is imperative that a patient lowers weight and liver volume prior to bariatric surgery.

Energy-Restricted Diets: VLCDs vs. LCDs

In order to lower weight and liver volume prior to bariatric surgery, an energy-restricted diet is routinely prescribed. There is however a lack of consensus regarding the optimal composition of this diet. A very-low-calorie diet (VLCD) and a low-calorie diet (LCD) are both popular hypocaloric diets that are widely advised. A VLCD is generally defined as an intake of 450-800 kcal per day, while an LCD implies 800-1500 kcal per day. The duration of very-low-calorie diets (VLCDs) varies between 10 and 63 days, and the consistency varies between exclusively liquid meal replacements or a combination of liquid meal replacement and food meals.

While very-low-calorie diets (VLCDs, 450-800 kcal per day) have shown to be effective, the effectiveness of low-calorie diets (LCDs, 800-1500 kcal per day) is less obvious.

Effectiveness of Low-Calorie Diets (LCDs) on Liver Volume Reduction

A systematic review aimed to elucidate the effectiveness of LCD on liver volume reduction in patients awaiting bariatric surgery. An LCD was effective in liver volume reduction (12-27%) and weight loss (4-17%), particularly during the first weeks, and showed acceptable patients’ compliance.

Read also: Diet Before Bariatric Surgery

Nine LCDs were included with varying dietary characteristics among eight studies. Left liver lobe volume showed a decrease of 11-29% and total liver volume showed a decrease of 12-27% with a mean of 16%. Six of the eight studies reported the pre and post LCD weight. The weight loss ranged from 5.4 to 23.6 kg, corresponding with a percentage original body weight loss ranging from 4.2 to 16.7% with a median of 6.0%.

Key Components of a Bariatric Liver Shrinking Diet

The goal of a bariatric surgery pre-op diet is to shrink your liver prior to surgery by depleting stored glycogen. The goal is to consume 2-3 meals of solid, macronutrient-rich foods per day. These whole meals will stay in your stomach longer, keeping you full. In addition, use protein shakes as a supplement snack, generally 1-2 protein shakes per day.

A liver shrinking diet is low in calories, carbohydrates, and fats. The carbohydrates we eat provide energy in the form of Glycogen, which our body stores in the liver and muscles. When we consume more carbs, the body stores more glycogen, but it doesn’t store it alone. Glycogen and water are stored together and every gram of glycogen grabs 3 grams of water to store with it. This leads to the enlargement of the liver. The more carbs consumed, the bigger the liver can be. The liver-shrinking diet is created to be high in protein and low in fat and carbs, so your body does not produce more glycogen and forces your body to pull it out of storage. The glycogen and water reduction causes the liver to shrink. For patients with higher BMIs, the liver will normally take longer to shrink.

Macronutrient Guidelines

Protein: High protein intake is crucial. Aim for 20-25 grams of protein per serving in protein shakes. Two 4 - 6 ounce servings of lean protein per day (chicken, turkey, fish, lean ground beef)
Carbohydrates: Significantly reduce carbohydrate intake to deplete glycogen stores in the liver. Limit fruit intake. The goal is to consume 2-3 meals of solid, macronutrient-rich foods per day.
Fats: Limit fat intake. 1 - 2 servings of healthy fat per day (salad dressing, olive oil, nuts, avocado, olives)

Approved Foods

Lean protein sources (chicken, turkey, fish, lean beef)
Non-starchy vegetables (as many as desired, excluding potatoes, corn, peas, squash, and pumpkin)
Limited healthy fats (olive oil, nuts, avocado)
Unsweetened almond milk or coconut milk
Protein shakes (at least 20 grams of protein, 5 grams or less of sugar)
You can have ½ a cup of berries, ½ a banana, or 1 apple daily for fruit

Foods to Avoid

Bread, rice, oats, pasta, refined grains, tortillas
Sauces with sugar
Dairy/plant-based milk, yogurt, cheese (except unsweetened almond milk and coconut milk)
Alcohol, marijuana, or THC products (two weeks prior to surgery)
Carbonated beverages (including sparkling water)
Sugary and starchy foods

Sample Meal Plan

Here is a sample of what your liver-shrinking diet might look like: In between meals drink water and other beverages that are on the approved list to equal at least 64 oz a day.

Breakfast: Options include 2 Whole Eggs, 1/2 an avocado, 1 Cup of Spinach (Raw or Cooked), or 1 Protein Shake
Mid-morning snack: 1 Protein Shake (limit 1-2 per day)
Lunch: Raw or cooked vegetables (you can add one TBSP olive oil or butter spray to veggies) and 4 oz. lean meat. Example: 4 oz (110g - 170g) of lean protein, 2 Fist size of vegetables (fibrous carbs), 1-2 thumb size of fats
Dinner: Salad with Protein (chicken, fish, egg, etc.), a small amount of no or low sugar dressing (preferably olive oil & vinegar or Lemon)
Evening Snack: Apple slices with Almond Butter or Vegetables with Hummus

You may also add 1 TBSP chia seeds to your shakes or take psyllium husk to help you stay satisfied throughout the day.

Read also: Bariatric Surgery Outcomes

Important Restrictions

Discontinue ALL consumption of Dairy, Starches, Sugars, Desserts, and Fruit (with the exception of 1/2 cup berries or 1/2 a banana daily)
Discontinue drinking ALL caffeine 2 weeks prior to your surgery date. Caffeine is a diuretic, may cause dehydration and is acidic. You may drink decaffeinated coffee. Please ensure to stay hydrated.
Discontinue ALL carbonated beverages (including sparkling water)
Avoid: Ginseng, Ginger, Garlic and Omega 3 supplements. These increase bleeding risk. You may consume small quantities of garlic and ginger in cooking
VERY IMPORTANT: Begin the practice of NOT drinking 30 minutes prior to/during/post meals. This should become a LIFELONG HABIT.

Protein Shake Criteria

Your bariatric clinic will often provide you with a list of “ready-made” protein shakes or powders that meet their criteria but the universal standards are as follows:

No more than 200 calories.
Contains between 20-25 grams of protein.
15 grams or less of carbohydrates.
5 grams or less of sugar.
< 10% of the daily recommended amount of total fat.

You can mix powdered supplements with unsweetened almond milk, unsweetened soy milk, 1% milk, or water. Do not add in extras, fruit, or avocado.

Duration of the Liver-Shrinking Diet

The duration of the liver-reduction diet will be determined by the bariatric surgeon performing your procedure. Many surgeons base the duration of the diet on the patient’s starting BMI.

BMI 35-39.9: 1 Week
BMI 40-49.9: 2 Weeks
BMI 50-59.9: 3 Weeks

It is recommended that an LCD provides 800-1200 kcal per day and that it lasts for 2 to 4 weeks. The largest decrease in liver volume was observed when an LCD lasted for two to four weeks. Previously, Edholm et al. demonstrated that liver volume decreased during the first two weeks with 18 ± 6.2% and no further change afterwards . Moreover, Gonzales-Perez et al. measured a decrease of 32% between baseline and week four after an LCD and a much smaller decrease (17%) between week four and six. These findings are confirmed by Colles et al. who demonstrated that 80% of total liver volume reduction occurred in the first two weeks.

Compliance and Tolerance

Six studies recorded compliance and tolerance of the LCD. The studies reported a generally high compliance of 80-89%. This study found that an LCD was well tolerated and that patients were highly compliant (80-89% compliance rate).

Compliance was measured in four different ways: (1) presence of ketonuria , (2) the combination of presence of ketonuria with weight loss , (3) formula sachets returned, and (4) unblinded patient interviews . Tolerance was measured in three different ways: (1) questionnaires , (2) unblinded patient interviews, and (3) unknown assessment technique .

Yet again, this data must be interpreted with caution because some studies determined compliance using subjective methods such as counting the returned empty formula sachets and interviewing patients in an unblinded manner.

Potential Risks and Mitigation Strategies

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.

This study found that 51% of the weight loss was contributed to LBM loss rather than fat mass loss. When comparing this finding with a VLCD, previous research showed that this resulted in an even larger LBM loss (62%). This indicates that an LCD leads to less LBM loss, but there are some notes of caution hampering firm conclusions. This review reported a high variety in results with two studies that showed a LBM loss of 23-29% and three studies that showed a LBM loss of 46-60% . Moreover, three studies measured body composition by bioelectrical impedance analysis which is prone to error . In future research, it is important to realize that LBM preservation not only relies on dietary composition but also on physical activity .

Minimizing Lean Body Mass Loss

To mitigate LBM loss, prioritize adequate protein intake and incorporate physical activity into the pre-operative plan.

Surgical Complexity and Outcomes

Mixed results on surgical complexity ratings were found. One study reported improvement of surgical complexity after LCD, while another study reported no change in surgical complexity. Surgical duration decreased in one study, while two studies found no difference.

Previously, van Nieuwenhove et al. demonstrated that, in a single-blinded RCT, a two weeks lasting LCD reduced perceived surgical difficulty and 30-day complications, without affecting the duration of surgery . Additionally, a Scandinavian study including over 22,000 patients showed that a weight loss of about 5% reduced the risk of overall postoperative complications in the range of 13-18%. The inconsistencies between these findings and the findings of this review might be attributable to insufficient power, lack of blinding by the surgeon and different dietary approaches.

Limitations and Future Directions

There are several limitations that should be considered when interpreting this systematic review. First, there was a large heterogeneity in terms of diet composition, diet duration and liver volume measurement. Second, different surgical techniques were used which may represent different populations. Third, the quality of the studies was limited with five observational studies being included. Fourth, a control group and blinding of assessor lacked in almost all of the studies which may have caused detection bias.

In the future, it could be questioned if all patients will actually benefit from a universal LCD. Perhaps preoperative diets would be better in a personalized way, depending on what goals are being set by a multidisciplinary team. These goals could vary between patients with different BMI’s or comorbidities, for example reduction in liver volume or stabilization of glucose levels.

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