Pre-op and post-op diets for weight loss surgery patients

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Protein is priority

Your pre-op and post-op bariatric diet will focus on protein, which is needed by your body to function properly, improve wound healing, maintain muscle tissue and avoid unnecessary hair loss.Protein, unlike fat and carbohydrates, is not stored by the body and must be consumed in sufficient quantities every day. Protein will be the top diet priority during recovery and for the rest of your life following weight loss surgery. In general, it's recommended that 10–35% of your daily calories come from protein.The Recommended Dietary Allowances (RDA) for women is 46 grams and for men 56 grams of protein each day¹.Your surgeon will have specific guidelines as to the amount of protein you should be eating daily. Your sex, BMI, and age are all factors that determine your daily needs for protein. Protein supplementation will be used as needed to reach your daily goal for protein.

Pre-op diets

Even before you undergo weight loss surgery, your bariatric surgeon may recommend a change in your diet to prepare your body for surgery. This special pre-operative diet will help shrink your liver and reduce fat in your abdomen so that your surgeon can operate more easily and safely and increases the chances of your surgery being performed laparoscopically.Losing weight before surgery will also help with your recovery, increase your rate of weight loss and aid with the transition to your post-op diet.The time frame for your pre-op diet will vary from patient to patient. Based on your situation and how much weight you need to lose before surgery, your bariatric surgeon will advise you when to start your pre-surgery diet.For gastric band patients, the pre-op diet may start two to three weeks before surgery, while for the more involved procedures such as gastric sleeve or gastric bypass your pre-op diet may start sooner.You can expect your pre-surgery weight loss diet to be high in protein, but low in calories, fats, and carbohydrates, especially refined sugars and saturated fat.The pre-surgery diet generally ranges from 800 to 1200 calories per day with about 70 to 120 grams of protein each day. You will also be advised to start vitamin supplements to ensure your body has the nutrients necessary for recovery and health.A few of the benefits of the pre-op diet include:• Shrinking your fatty liver• Preparing your body for surgery• Faster recovery following surgery• Preparing you for your post-operative diet

The liver shrinking diet

The liver shrinking diet is an eating plan low in dietary carbohydrate and fat that will encourage your body to use up glycogen (a form of sugar that is stored in the liver and muscles for energy) and fat stores to help shrink the size of your liver.With each ounce of glycogen your body stores three to four ounces of water². When you follow a very strict diet that is low in starch and sugars your body loses its glycogen stores and some water resulting in your liver shrinking.This diet is only recommended before surgery and is not to be followed post–operatively.It is quite possible that you will lose a lot of weight following the liver shrinkage diet but it will mainly be water loss. This diet usually allows between 800 to 1000kcal a day.By reducing the size of the liver, the operating time for laparoscopic surgery is shortened and the procedure is safer.In some instances, a bariatric surgeon may postpone surgery if the patient's liver is too large.

Weight loss recovery diet

After bariatric weight loss surgery, whether you have an adjustable gastric band put in place or undergone a more complex operation such as the gastric sleeve or gastric bypass procedure, it will take time for your body to heal. As your body recovers from surgery, it is essential for you to follow the specific eating guidelines given to you by your bariatric surgeon or dietician/nutritionist. The bariatric recovery diet is set to ensure that your body heals properly and obtains adequate nutrition.

Post-op diet progression

Immediately following weight loss surgery you will not be able to eat much of anything. The post-op recovery diet will slowly progress from clear liquids to full liquids, pureed food, soft foods, and then you will finally be able to start eating solid foods.No matter the procedure, it is important to progress gradually through the post-op diet so your body has time to heal from surgery and you can adjust to the changes.If you don't follow the post-op diet progression plan, you can:• disrupt the healing process• increase the risk of surgical site complications• experience more pain• cause vomiting• dislocate the band (for gastric band patients)Take time to heal and don't try to rush recovery!

Diet Phases:Phase 1 – Liquids

• Clear liquid diet: At first, you will only drink clear liquids. Clear liquids are liquids that you can see through, such as water, tea, diluted non-acidic fruit juices (apple, grape, cranberry), broth (beef, chicken, vegetable), protein fruit drinks, sugar-free gelatins, and artificially sweetened non-carbonated drinks.• Full liquid diet: After the first phase you will progress to full liquids. These are fluids you cannot see through, such as low-fat cream soups, protein shakes and skimmed milk.

Phase 2 - Soft foods

• Pureed food diet: Pureed foods do not contain any chunks and have been blended into the smooth consistency of baby food. At this stage chunks of food can get stuck in the stomach opening and cause pain and vomiting. To puree foods, combine high-protein foods with broth, skimmed milk or low-calorie sauces in a blender and puree until smooth. Other options might include pureed soup or cottage cheese.• Soft food diet: You will gradually move on to soft foods, which are foods with texture but tender and easy to chew. Soft foods might include ground or finely diced meats, fish, canned or soft fruit, scrambled eggs and cooked vegetables.

Phase 3 - Solid foods

• Solid food diet: Once your body has healed, your bariatric surgeon/ dietician or nutritionist will put you on a regular bariatric diet. Meals should always include high-protein food items such as lean meat, yoghurt, eggs, whole grains, fruits and vegetables.

Top tips to following a post-operative bariatric diet:

• Aim for three small meals a day³.• Limit snacking between meals to one to two times per day and only eat low calorie, healthy snacks such as fruit, vegetables, low fat yoghurt.• All meals should be eaten slowly and food should be thoroughly chewed. Aim for about 15 chews per bite so that the food turns to mush and about 25 minutes for each meal.• Eat the protein foods first as these are the most important.• Eat solid food. While soft foods may be easier to digest, they usually contain more carbohydrates and fat and make you feel less full than solid foods.• When you feel full or tightness in your chest, stop eating, even if you haven't finished your meal.• Don’t eat and drink at the same time. This can flush food out of your stomach pouch and make you feel less full or it can overfill your pouch leading to vomiting and stretching.• Since the amount of food eaten each day is very limited, every bite counts. It is important to eat only healthy and nutritious food.


Most bariatric diets allow 1000 to 1200 calories per day with meals focused on lean sources of protein, whole grains, fruits, and vegetables.


Ideally you should aim to have three small portions each day. Eat the protein part of the meal first, in case you feel full. Meals will primarily consist of protein-rich foods, including lean meats (chicken, turkey, fish), low-fat dairy products (yogurt, cottage cheese), eggs, and soy products. Include a variety of nutrient-rich fruits and vegetablesProtein is particularly important after a gastric bypass and sleeve gastrectomy as you have greater wounds to heal than band patients.


Aim for 1.5 litres of low calorie liquids per day⁴. Try to avoid drinking high-calorie drinks, such as cola, alcohol, sweetened fruit juices and milkshakes. These types of drink will quickly pass out of your stomach and into your small intestine, increasing your calorie intake.Post-operatively, one of the main challenges for a gastric bypass patient over time is to maintain hydration. You will only be able to drink one to two ounces of fluid at a time but your body still requires the same amount of fluid as before the surgery.The best way to achieve your fluid goals each day is to take small amounts of fluid on a near-constant basis. Carry along a bottle of fluid with you at all times.

Diet after a gastric balloon

To get the best results from your gastric balloon procedure it is crucial that you understand and follow a strict post-operative diet. A gastric balloon is a very effective weight loss solution, but you must adhere to some important dietary choices in order for it to be as successful as possible.Shortly after insertion of the balloon you will be asked to sip water. If that is tolerated then you can progress onto clear liquids and then full fluids for three days. You should aim for at least eight cups of fluids daily. Your liquid diet will help you adjust to the balloon, prevent dehydration and keep your energy levels up. You should avoid solid foods at this stage as they may cause nausea and vomiting.On day 4 you can progress on to soft foods. Aim to have 4 small meals a day. If you are tolerating soft foods and liquids well then you can progress on to a normal textured diet on day 10. Some foods can stick to the balloon such as pasta. It is advisable to drink a few sips of water shortly after your food to rinse off the balloon.Your calorie intake must remain at a maximum of 1000 to 1200 kcal per day.

Diet after a gastric band surgery

Typically following the insertion of your gastric band you will start with 2 weeks on a liquid-only-diet initially being clear liquids then progressing to full liquids. During the next 2 weeks you will only be able to drink liquids and eat small amounts of pureed food. Attempting to eat solid foods at this stage could put pressure on the band and damage it.In weeks 4 to 6, you can you have soft food. After 6 weeks you can gradually resume a healthy diet based on eating small amounts of nutritional solid food that you will need to stick to for the rest of your life.Due to the position of the band, you will probably experience a feeling of fullness or tightness in your chest rather than in your stomach. If you experience repeated episodes of vomiting after eating, it may be a sign that you are eating too much or that your band needs to be adjusted. At 6 weeks your band will be adjusted to ensure it is not too tight or too loose.Your calorie intake will normally be between 1000 to 1200 kcal per day.

Diet after a gastric sleeve surgery

Following your sleeve gastrectomy you should take small sips of liquid throughout the day and pay attention to the feeling of fullness. Once you tolerate liquids, you will be able to start on pureed foods. It may only take a few days to advance from liquids to pureed foods, but this stage can last weeks.After pureed foods are well tolerated and healing has progressed, you will be able to start adding soft foods to the diet. This is generally sometime around 4 weeks after surgery. New foods should be added to the diet one at a time to observe your reaction to it.After 6 weeks you should be able to resume a normal solid food diet. The gastric sleeve will allow you to eat almost any type or texture of food.Your calorie intake will be between 1000 and 1200 kcal per day.

Diet after a gastric bypass surgery

Immediately after your gastric bypass surgery your diet will be limited to liquids. Recovery will vary from patient to patient but it can take up to 3 months for your body to heal.In the first couple of weeks after surgery you will drink liquids starting with clear fluids and moving on to full liquids as your body tolerates them. In week’s 2 to 4, you can eat pureed food and by week 6 you may be able to eat soft food. After 6 weeks, gradually resume eating a healthy diet.After gastric bypass diet, eating is focused on providing the body with healthy proteins and nutrient rich foods. You will need to avoid eating food that is high in sugar, such as chocolate, cakes, sweets and biscuits as your bypass will affect how you digest sugar and if you eat these foods you may suffer from dumping.You will also need to take daily vitamin and mineral supplements, as your small intestine will no longer be able to digest all the vitamins and minerals your body needs from your diet. This varies from person to person but most people are required to take:• a multivitamin supplement, which contains a combination of different vitamins• a calcium supplement (the body requires calcium to maintain healthy bones)• an iron supplement⁴You will be advised to consume 800 to 1000 kcal for the first 1 to 2 years during weight loss and then 1000 to 1200 kcal per day thereafter for weight maintenance.

Understand your eating triggers

It’s important to take time to consider and understand your current eating habits before you have bariatric surgery. Appreciating the emotional triggers for your eating, also known as head hunger, may help you establish and maintain new eating habits after surgery that listen to your physical body hunger instead of head hunger.Here are a few examples of head hunger and strategies to help you break the emotional associations that lead you to overeat.a) GrazingIt is common for people to eat snacks throughout the day in place of full meals. Your post-op bariatric diet will need you to stick to 3 meals a day and up to 2 healthy snacks.If you are used to snacking during the day you will need a strategy in place to distract you from grazing such as calling a friend, exercising or reading a favourite magazine.b) Seasonal and weather related cuesIf it’s cold outside you may comfort eat. You may have social ties of special seasonal activities that can lead to bigger portion sizes. Being aware of these will help you really listen to your body, follow your eating plan and help you eat special foods mindfully.c) Forbidden food syndromeThe thought of dieting can trigger feelings of deprivation and cravings and it has been shown to increase food intake⁵. Try not to talk about food, weight and dieting too much and depend on your physical hunger cues to let you know when it’s time to eat.d) EmotionalEmotions are common triggers for eating. People sometimes eat to cope with stress, boredom, anger, anxiety and loneliness. Overeating to deal with these feelings leads to weight gain whilst denying you the opportunity to satisfy your true needs. Try to figure out what you need that drives you to eat when you aren’t physically hungry. Once you’ve identified these emotions seek ways to comfort, nurture, calm and distract yourself without turning to food.Here you can find our guide prices for bariatric surgery.Read more weight loss surgery blog posts to find answers to the most common questions including: pros and cons of gastric balloon and gastric sleeve, how to choose a weight loss surgeon,exercise after weight loss surgery, cosmetic surgery after weight loss surgery etc.

About Ramsay pre and post-operative bariatric diets

Ramsay Health Care is a leading provider of weight loss surgery in the UK. Ramsay offers weight loss procedures performed by experienced bariatric surgeons who are highly qualified and have undergone intensive specialist training.At Ramsay Health Care your weight loss surgeon will work in a multidisciplinary team who liaise with each other to provide the best plan of action for you. They include a dietitian who will meet with you and produce a bespoke eating plan, and specialist trained nurses who will be by your side during your journey to offer support and guidance to ensure that you achieve your goals.Contact us for more details.


¹² http://www.bospauk.org³ http://www.obesityaction.org⁴⁵

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