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Gastric Sleeve Diet


If you are planning to have gastric sleeve surgery you will need to follow a specific and strict diet that starts two weeks before the procedure.

Your gastric sleeve pre-op diet aims to reduce your liver size and weight to make the operation easier.

Your gastric sleeve post-op diet will help you to recover from surgery and avoid complications.

You will move through the post-op diet stages of liquids, pureed and soft foods, to a final diet of healthy protein rich, low calorie solid foods that you will need to continue for life to achieve and maintain your weight loss goals.

The success of your gastric sleeve surgery will depend on your ability to stick to a healthy diet and lifestyle.

Your bariatric team will give you information on your gastric sleeve diet and offer support throughout your weight loss journey.

Pre-gastric Sleeve Diet

If you are overweight, your liver will be too. Your liver is found right next to your stomach, so a larger liver makes gastric sleeve surgery more difficult and increases your risk of complications.

Your liver can shrink in size very quickly. If you follow a strict pre-op diet two weeks before your scheduled gastric sleeve surgery date, your liver will shrink and your procedure will be safer, quicker and easier. This diet also prepares you for your gastric sleeve post-op diet.

A gastric sleeve pre-op diet typically reduces your calorie intake, lowers your carbohydrate consumption, and eliminates sugar from your diet. Two days before your surgery, you can expect to move to a clear liquid diet avoiding caffeine and carbonated drinks.

It is important that you follow your weight loss surgeon’s recommended two-week gastric sleeve pre-op diet. Your surgeon may also recommend that you take daily bariatric multivitamins to ensure your body gets all the nutrients it requires.

Post Operation Diet

After your gastric sleeve operation your body will need nutrients to heal your wounds and help you recover fully.

You will pass through five phases of eating that include: clear liquid, full liquid, pureed, soft food, and finally an ongoing protein-rich nourishing diet. You can expect to spend around one week in each phase. You should not skip phases.

Week 1 – Clear Liquids

During the first week after your gastric sleeve surgery you will continue with the clear liquid diet you started a couple of days before your operation. This will give your body time to heal and help avoid post-op complications such as diarrhoea, constipation, and dehydration.

You may think it will be hard to stick to a clear liquid diet but often people feel little or no hunger immediately after their gastric sleeve surgery.

You should start with sips of clear liquid to avoid becoming nauseated. You can gradually increase the amount you take in one go. You must make sure you drink plenty of clear liquid to avoid becoming dehydrated. You should aim to drink a minimum of 2.5 litres over the course of each day. Drink from the time you get up in the morning and throughout the day until you go to bed.

For the first two weeks after surgery, you will be recommended to take vitamin supplements in a chewable or soluble form. Your surgeon will give you further advice on vitamin supplements.

Clear liquids can include:

  • Water
  • De-caffeinated coffee or tea including herbal, fruit, and green.
  • Clear broth such as chicken, beef or vegetable.
  • Marmite or Bovril drinks.
  • Diluted fruit juice such as apple, grape or cranberry.
  • Diluted sugar-free squash.
  • Sugar free drinks, flavoured water and popsicles.

What you should avoid:

  • Caffeine – may contribute to acid reflux and dehydration.
  • Sugary drinks – may result in nausea, fatigue, diarrhoea, and even vomiting. Sugar is also full of empty calories.
  • Carbonated drinks – may contribute to gas and bloating.

Week 2 – Full Liquids

During the second week after your sleeve surgery, you will continue to drink plenty of clear fluids whilst also incorporating into your diet fuller liquids that are rich in protein. Your appetite may increase but your digestive system is not yet ready to handle solids. You should fill up on a variety of nutritional liquids. 

Full liquid choices in addition to your clear liquids include:

  • Low fat milk - semi-skimmed or skimmed. Milk can be flavoured with a low-calorie hot chocolate.
  • Homemade smoothies.
  • Slimming drinks and shakes.
  • Yogurt drinks.
  • Smooth soups such as cream of tomato, chicken, or oxtail.
  • Sugar-free, non-fat plain Greek yogurt, frozen yogurt.
  • Fat free, no added sugar ice cream
  • Sorbet.

You should still avoid caffeine, sugary drinks and carbonated drinks.

Additional foods to avoid include:

  • Sugary foods.
  • High-fat foods such as whole-milk yogurt.
  • Food that has any lumps.

Week 3 – Pureed Foods

As you reach the end of week two and move into week three you can start to add some “real” but pureed food to your diet. You need to ensure you eat 60 grams of protein each day so include protein in each meal. You can try adding milk when you blend your foods, ensuring that it is free of lumps and a yoghurt like texture.

You may find it tough at this time. Try to eat small portions slowly. Re-introduce new foods slowly, giving your body time to react to each new food so that you can identify any foods that are disagreeable and cause gas, stomach upset, or diarrhoea.

Once you can tolerate pureed foods you can choose a complete A-Z vitamin and mineral supplement in a tablet form, to help prevent nutritional deficiencies such as iron, folate, vitamin D, and calcium deficiencies.

Pureed foods can include:

  • Soggy Weetabix or Ready Brek.
  • Mashed fruit - bananas, avocados, and canned fruit. Be careful of their sugar content.
  • Blended steamed fish in a low-fat sauce.
  • Canned tuna and salmon – try adding low fat mayonnaise.
  • Mashed sweet potato.
  • Humous.
  • Low-fat cottage cheese and soft cheeses.
  • Liquidised meat or fish stew.
  • Liquidised steamed or boiled vegetables.
  • Thick blended soups.
  • Scrambled eggs.
  • Ground chicken or beef.

Additional foods to avoid include:

  • Food high in starch such as pasta, rice and bread.
  • Tough, raw vegetables such as broccoli, asparagus, celery, and leafy greens.
  • Skin and seeds from vegetables and fruits.
  • Fatty foods including oils and butter.
  • Spicy food.

Week 4– Soft Foods

At week four you can start to add soft foods and lumps to your diet. You can also re-introduce caffeinated drinks, in moderation, at this time.

Soft food ideas to add to your diet include:

  • Well-cooked chicken and turkey
  • Soft fish
  • Lean mince meats
  • Well-cooked vegetables
  • Low-fat cauliflower cheese
  • Eggs, including scrambled, poached, or hard-boiled
  • Soups with lumps
  • Canned or soft fruit
  • Sweet potatoes
  • Rice
  • Low-fat cheese
  • Low-sugar cereal

Additional foods to avoid include:

  • Hard-to-digest foods such as steak, tough vegetables, and nuts.
  • White potatoes.

Week 5 Onwards – healthy diet

By week five you can eat solid food safely. You can use your new eating plan as a template of healthy eating for life.

Your new diet needs to be low in fat, low calorie, and portion controlled. Your bariatric team will offer advice and support for your new diet.

Keep introducing new foods and monitoring any reaction to them. Avoid empty calorie foods that do not have any nutritional value. Try to keep to three small meals a day and minimal snacks. Don’t forget to keep yourself hydrated.

Healthy diet foods include:

  • Lean meat, poultry, and fish.
  • Low-fat dairy products.
  • Steamed or raw vegetables and fruits.
  • Good starches and whole grains.
  • Fats in small quantities.

Additional foods to avoid include:

  • High calorie foods and drinks.
  • Sugary sweets and soda.

Long term diet tips following gastric sleeve surgery

You will need to continue eating a healthy, high protein, low fat, calorie-controlled diet for the rest of your life to achieve and maintain your weight goals.

Some top tips include: 

  • Keep to three small meals a day.
  • Have protein in each meal and eat it first.
  • Introduce new foods one by one.
  • Take a tablet form daily vitamin and mineral supplement as directed by your bariatric team. You will also require vitamin B12 injections (1mg) once every three months.
  • Eat slowly and chew your food thoroughly. The more you chew, the easier your food is to swallow and digest.
  • Plan your meals so you are not tempted by off-diet foods.
  • Drink plenty of water and always have some water to hand.
  • If you feel hungry between meals try taking a drink first as your body may be mistaking hunger with thirst. If you are still hungry then have a small snack such as a piece of fruit or a low-fat yoghurt.
  • Ask for half portions at restaurants – it may be discounted and it will prevent you from being tempted to overeat.

Foods to avoid: 

  • Food with empty calories – make wise diet choices and avoid foods with little or no nutritional value.
  • Alcohol - is high in calories and your alcohol absorption will dramatically increase after surgery.
  • Fizzy drinks - as they cause bloating and can increase your small stomach size.
  • High fat foods – they may make you feel nauseous and will not help you to lose weight.
  • Tough meats - are hard to chew and hard to digest.

Things to avoid: 

  • Avoid eating and drinking together - wait at least thirty minutes between eating and drinking. Drinking fluids with meals may lead to an overfull stomach and vomiting. It can also stretch your stomach and “wash” your food through too quickly so that you don’t sense the early signs of fullness and may lead to over eating.
  • Avoid overeating - stop eating when you feel satisfied. Overeating will stretch your stomach pouch and may make you vomit.

Avoid grazing - this often adds extra calories to your controlled diet. It also interferes with your body’s ability to burn fat as insulin levels will be consistently raised

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  • Access to a team of specialist bariatric nurses – expert medical advice and regular medical reviews
  • Access to the hospital out of hours service
  • Access to a dietician - expert nutritional advice on making the most of the procedure you have chosen to have
  • 2 x-ray adjustments and up to 6 clinical adjustments
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