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Bariatric or weight loss surgery can be an effective treatment for obesity and other conditions that tend to occur with it like diabetes, high blood pressure, and acid reflux.
In preparation for the procedure, bariatric surgeons usually prescribe a low-calorie diet — sometimes called a liver shrinking diet — that is intended to shrink the liver and improve surgery outcomes.
This article explains how the liver shrinking diet works, what the diet allows, its benefits and risks, and provides a sample 3-day liver shrinking diet menu.
What is the purpose of shrinking the liver?
A liver shrinking diet is a low-calorie diet intended to shrink the liver and decrease fat stored around it.
The liver is a vital organ that removes toxins from the blood, maintains healthy blood sugars, and makes important proteins, among other functions.
Fat can form in and around the liver due to:
- being overweight or obese
- having type 2 diabetes or insulin resistance
- having high cholesterol or triglycerides
- frequent alcohol use
Weight loss surgeons commonly prescribe a liver shrinking diet to make it easier and safer for them to perform weight loss surgery (1).
There are four main types of weight loss surgeries (2):
- Gastric sleeve. In this surgery, a surgeon removes most of your stomach.
- Gastric bypass. This surgery involves creating a small pouch from the stomach and connecting this pouch directly to the small intestine.
- Adjustable gastric band. In this surgery, a surgeon places a ring with an inner inflatable band around the top of your stomach to create a small pouch.
- Biliopancreatic diversion with duodenal switch. This is a more complex and less common procedure that combines components of the gastric sleeve and bypass.
Surgeons typically prescribe the diet at least two weeks before surgery, but some patients may need to follow it longer if they have a lot of fat in and around their liver.
A few days before the surgery, a clear liquid diet is usually recommended followed by nothing by mouth on the day of surgery.
The diet must be followed very closely as going off-plan or “cheating” too much could delay the surgery or increase the risk of surgery complications.
Liver shrinking diet guidelines
Liver shrinking diets can be categorized as low- or very-low-calorie diets (VLCDs).
VLCDs contain 450–800 calories while low-calorie diets contain 800-1,200 calories per day (3).
Due to their severe caloric restrictions, VLCDs are usually only prescribed under direct medical supervision in an inpatient setting.
However, compared with a low-calorie diet, a VLCD can result in a greater loss of lean body mass and is associated with more severe side effects like extreme hunger, nausea, diarrhea or constipation, and dizziness (3).
As a result, a low-calorie diet that contains 800 to 1,200 calories per day is preferred and recommended for decreasing body fat and shrinking the liver before surgery.
Most of the calories should come from protein with limited amounts of carbs and fats.
Here are the general nutrition guidelines for a liver shrinking diet:
- Calories: 800-1,200
- Protein: 80–100 grams
- Carbs: 40–80 grams
- Fat: 40–50 grams
- Fluids: 64 ounces
The diet usually includes at least 3 meals, and if needed, 1–2 snacks per day.
Portion sizes are important to stay within the 800–1,200 calorie limit of the liver shrinking diet.
Here are the portions sizes for meals:
- 2–4 ounces of lean protein
- 1–2 cups of non-starchy vegetables
- 1/2 cup of starch
- 2 tbsp of oil
High protein shakes are commonly used to replace one or more meals to meet the nutrition guidelines for a liver-shrinking diet.
These protein shakes may be a powder that you mix or they can come pre-made.
These protein shakes should contain:
- 20 grams or more of protein
- 3 grams of sugar or less
- 5 grams of fat or less
- Less than 200 calories
Foods to eat and avoid
A liver-shrinking diet includes foods that are high in protein and low in calories and carbs.
Foods to eat
Here is a list of foods that are generally approved:
- Fruits: apples, berries, bananas, grapes, oranges, etc.
- Non-starchy vegetables: arugula, asparagus, broccoli, cabbage, carrots, green beans, kale, lettuce, mushrooms, peppers, tomatoes, etc.
- Starchy vegetables: beans, jicama peas, potatoes, squash
- Grains: brown rice, oatmeal, whole-grain bread
- Poultry: eggs, boneless chicken breast, turkey sausage
- Meats: lean cuts of beef and pork that contain the words “loin” or “round”
- Seafood: crab, haddock, pollock, tilapia, salmon, shrimp
- Low-fat dairy: skim of 1% milk, low-fat cottage cheese and yogurt, cheese
- Oils: canola and extra-virgin olive oil
- Beverages: black coffee, tea, and approved protein shakes
Here is a list of a few approved protein shakes:
- Premier protein shake
- Ensure Max shake
- Bariatric Advantage powder
- Orgain Clean Protein shake
- Boost Max Glucose Control shake
- Optimum Nutrition Whey Protein powder
Foods to avoid
Here is a list of foods that should typically be avoided:
- Refined grains: most breakfast cereals, biscuits, crackers, desserts, pastries, white rice, tortillas, and pasta
- Highly-processed foods: boxed pasta meals, chips, fast food, fried foods, frozen dinners, pizza, potato chips
- Sweets: candies and chocolate
- Dairy: 2% or whole-fat milk, flavored milks, flavored yogurt, ice cream, or other dairy desserts
- Beverages: alcohol, fruit juice, sugar-sweetened beverages like regular soda, energy drinks, sports drinks, teas, and coffee
3-day sample menu plan
Here’s a 3-day sample liver shrinking diet menu plan, with each day containing fewer than 1,200 calories:
- Breakfast: Premier Protein shake and one apple
- Lunch: Premier Protein shake and 1/4 cup walnuts
- Snack: 1 cup non-fat cottage cheese and 1/2 cup sliced peaches
- Dinner: 3 cups of salad mix with 4 ounces of grilled chicken and drizzled with 2 tbsp of classic French vinaigrette
- Breakfast: Ensure Max shake and 1 cup of blueberries
- Lunch: 2 ounces deli turkey meat, cheese slice, tomato, and lettuce on 1 slice of whole-grain bread
- Snack: 6 ounces non-fat Greek yogurt and 28 almonds
- Dinner: Ensure Max shake and 1 cup of roasted brussels sprouts made with 2 tbsp olive oil
- Breakfast: spinach omelet made with two whole eggs
- Lunch: Bariatric Advantage powder shake and apple slices
- Snack: string cheese and 1 cup of strawberries
- Dinner: 4 oz salmon, 1/2 cup cooked brown rice, and 1 cup green beans sauteed with 1 tbsp olive oil
Studies have shown that a liver shrinking diet can decrease liver size by 11–23% and decrease body weight by 4–7% after just 2 to 4 weeks (3).
Some of these decreases in liver size and bodyweight are probably related to a loss of stored carbohydrates — known as glycogen — and water but also due to a loss of fat and reduction in liver inflammation that causes the liver cells to balloon (4).
Indeed, one study found a 12% decrease in liver size — in part due to a 40% decrease in stored liver fat — after four weeks of following a liver shrinking diet (5).
What’s more, one study found that following a liver shrinking diet at least two weeks before weight loss surgery resulted in greater weight loss and improvements in liver function six months post-surgery (4).
The diet can also be effective for fat loss and improving liver health in people who aren’t planning to receive weight loss surgery.
This is because the diet contains much fewer calories than most people’s needs and it’s rich in protein.
There are few risks associated with the liver shrinking diet when followed as part of the preoperative weight loss surgery plan.
However, you may experience side effects due to the diet’s low-calorie allowance.
Common side effects include:
- low energy
- low sex drive
- constant hunger
- poor sleep quality
- hair thinning
- cold intolerance
While these side effects are generally minor, they can significantly interfere with work or school performance and relationships with family and friends, especially when you follow the diet for more than a few weeks.
Due to the diet’s restrictions, it can also be difficult to follow long-term, making weight regain a strong likelihood if you’re following the diet without intentions of receiving weight loss surgery.
People who follow the diet before weight loss surgery usually receive support from a registered dietitian, which can help improve diet adherence and accountability.
Finally, like any low-calorie diet, it can be deficient in certain vitamins and minerals, which can pose health problems when followed for more than a few weeks.
The bottom line
The liver shrinking diet is a low-calorie, high-protein diet designed to shrink the liver and promote fat loss.
It’s generally prescribed by weight loss surgeons at least two weeks before surgery to improve the safety and health outcomes of the procedure.
While effective for shrinking the liver and promoting fat loss, the diet can cause mild adverse side effects, it can be difficult to follow long-term, and it’s likely lacking in certain nutrients.