Roux-en-Y Gastric Bypass Diet and Nutrition Guidelines

by Sharon George, MS, RD, CDN

Welcome to the wonderful, amazing world of weight loss surgery! This is a very exciting time for you. You have spent the better part of your life between diets and have made the courageous decision to take back control of your life. There are many things that are important to understand and learn before you undergo the surgery you have chosen. This diet and nutritional section will guide you and answer many questions you have thought of, and some you may not have thought of yet. Your first big decision is to commit to undergoing weight loss surgery (WLS) and choose a surgeon you are comfortable with. Then it is time to find who will be your new best friend for at least the next eighteen months?your dietitian. She/he will walk you through each of the many stages you will be experiencing pre-operatively and post-operatively. This is a great time to increase your health as well as optimizing your future lifestyle. Be excited for your own personal journey to the best you can be!

The facts: The average person will lose to a point 30% or so above their Ideal Body Weight. About half of this weight loss occurs over the first three months after surgery, and will continue through eighteen months after surgery. Deciding to begin this process means that you are determined to improve your medical health. The table below explains in what areas you can expect improvement: 

Very likely to improve or resolve after WLS Good chance of improvement after WLS Unlikely to improve after WLS
  Congestive Heart Failure (CHF) Depression



Vascular Disease
High Blood Pressure (HTN) Urinary incontinence Arthritis
Obstructive Sleep Apnea Menstrual irregularity.
Infertility (women)
Organ damage due tress is decreased

GI Reflux (GERD)

Back pain


Knee pain



Bariatric surgery alters the digestive process. The operations promote weight loss by closing off parts of the stomach to make it smaller (volume restriction). This article is template because each person undergoing this surgery is a unique person with different healing qualities and different starting points.

Interesting fact: The average stomach (before surgery) can hold about three pints of food at one time. It can expand to the size of a football! After surgery, the amount of food your stomach can hold will be greatly reduced.

Getting started?

The Body Mass Index (BMI)
The BMI is a way to calculate the amount of weight a person is, compared to weight and body surface area. It is the standard that life insurance companies use to determine how at risk you are for death based on your weight. You are considered obese with a BMI over 30, morbidly obese over 35, and severely morbidly obese with a BMI over 40 or 100 pounds or more over your ideal body weight. A healthy BMI is considered to be 25 or less. Depending on your starting point your dietitian can help you figure out a realistic goal weight after surgery. 

The Pre-op Nutritional Consult
Have no fear. This is your easiest consult. We only ask questions and educate! It is recommended to see your dietitian as early in the process as possible so you can learn some good techniques to practice before surgery. The idea is to start being healthy before surgery. The following are common questions you will be asked during your interview. Think about these questions before you have your appointment to increase communication between you and your dietitian.

  • Height, weight, age, sex, body frame
  • Past medical history
  • Prescribed medications as well as anything over the counter or herbal
  • Compliance with medications
  • Special dietary needs (Kosher, vegetarian?)
  • Intolerances or allergies to foods
  • Daily meal patterns and food preferences
  • Fluid intake
  • Preparation of meals (homemade, dining out, fast food?)
  • Eating habits (daily meals consumed, daily snacks?)
  • Alcohol consumption
  • Weight loss history (age onset, diets, medications?)
  • Family history (obesity, diabetes?)
  • Personal experience with an eating disorder
  • Activity/ Exercise
  • Occupational physical limitations
  • Support system
  • Desired goal weight

Once you and your dietitian have discussed the above topics, she/he will go through the education portion of your consult. You will learn the guidelines that are required for you to follow after surgery. 

Pre-operative Nutrition
You all come from different backgrounds of eating difficulty. Your relationship with food and the years of trying to deal with it vary. You have now selected a surgeon and together have decided on which surgery is right for you. Your surgeon may have their own requirements for you before surgery. Some may require pre-op weight loss, others may want you on a liquid diet before the big day. You might ask your surgeon about their specific protocols.

You can do many things in preparation for your surgery to promote good health. The following are general guidelines for you to follow in the time you have, once you have committed to have the surgery, up until your surgery date. Make smart choices from every food group:

  • Eat good, quality protein. Select lean protein from different sources to incorporate into your meals (animal, plant, legumes, dairy, fish, poultry, eggs, and nuts).
  • Eat foods low in saturated fats, trans fats, cholesterol. Eat fats that are polyunsaturated and monounsaturated. Keep your total fat intake between 20-35% of total calories.
  • Limit sugar. If sugar is one of the first three ingredients on the list, don?t eat it.
  • Use the food label. Check the serving size and calories. Look to see how many servings you are actually consuming. Look at the %DV. If you are limiting something in your diet make sure it is 5% or less. Trying to increase fiber- select foods that are 20% or higher. How easy is that to identify the healthy foods?
  • Snack on fruits. Pick different colors. Make it interesting. Try one that you have never tried before.
  • Eat three meals a day. No skipping! Emphasize eating fruits, vegetables, fat-free or low fat dairy products, and whole grains (fiber).
  • Increase drinking water.
  • Increase daily physical activity. This needs to be discussed with your doctor. Different weights require different physical activity in order to be safe.
  • Maintain or lose weight. Do not gain weight prior to surgery.

Now that you have made some healthier food choices, maybe lost a few pounds, now you can walk into your surgery knowing that you are ready!

Interesting fact: If you eat 100 more calories a day than you burn, you will gain about 1 pound per month. That is about 10 pounds a year! 

The Hospital Stay
Okay. This part I can understand is no ones favorite part. Just think, now that your surgery is over, the recovery part you have everything to do with. What can you expect during your on average two day stay? The day of your surgery you will continue to be NPO (nothing by mouth). The following morning your surgeon may perform a GI study to detect if you have any leaks. (We call it, very professionally?the leak study!) Once you have been cleared that your new stomach pouch does not have any leaks, you will return to your room. Shortly a delicious tray of clear liquids will be brought to you. The post-op diet varies among surgeons, so check with your doctor.

Post Operative Diet

Stage I Diet (Liquids)
The only liquids you will consume are clear, sugar free liquids. You will usually receive a liquid diet and a protein supplement after surgery. Now it is very common to be afraid to take those first few sips, but remember, the sooner you tolerate your foods the quicker you get to go home. Your tray may vary from hospital to hospital, but it will generally have some water, clear broth, diet jello, and some sugar free juice or decaffeinated tea. The portions may be regular size, but you will be given a small medicine cup to drink out of. Usually, the standard is you can consume about ½ cup (4 ounces) every waking hour. This gradually improves with time. There will be no straws on your tray. Using straws post-operatively can increase gas problems and make you more uncomfortable. We recommend that you try to sip small amounts of your liquids, because your health care team want to see that you are able to tolerate it. Once it is decided by your surgeon that you can advance to the next stage, you will receive Full Liquids. This includes fat free cream soup, pudding, cream of wheat cereal or oatmeal and sugar free plain yogurt (no fruit). Take your time. Be persistent. Follow what your surgeon and nurses advise you to do and you will be discharged home. Many surgeons will send you home once you have tolerated a stage I diet. Other surgeons may keep you on liquids for awhile longer. The stages will be discussed in the next section. The recommendations for progression are individual by surgeon.

Stage II Diet (Soft, mushy and/or pureed)
This next stage can only start once you have successfully tolerated Stage I. You will only be allowed to consume foods that are NOT solids for the next 4-6 weeks (may vary by surgeon). Your goal is to eat approximately 550-700 calories a day and at least 60 grams of protein. Your new stomach pouch can only handle 1-2 ounces (the size of 1-2 ice cubes) at a time. It is up to you to try and eat a variety of foods and concentrate primarily on proteins. The following are good examples of food choices:

  • Cottage cheese 
  • Yogurt 
  • Egg whites beaters
  • Tofu products
  • Ricotta cheese 
  • Soft cheeses 
  • Hummus
  • Soft flaky fish 
  • Tuna
  • Ground meats 
  • Oatmeal Skim or 1% milk Pudding

These foods should meet the 5% rule for carbohydrates and fat. Some patients for convenience try jarred baby foods (meats). A general rule is to avoid red meats for the first 3-6 months. They are not easily tolerated. Ground meats such as turkey, chicken or veal should be tried, depending on your preference. Other foods that fit into this consistency are soft bananas, pureed melons, and overcooked vegetables. We do not enforce those types of foods, because they do not provide substantial protein.

Stage III (Regular)
Once again, you can only advance to this stage once Stage II has been completely tolerated. Regular solid foods should not be tried prior to 4-6 weeks after surgery. Remember, no liquids with meals! Continue Stage II foods and slowly introduce solid foods each day. Experiment with caution and slowly so you can easily tell which foods are tolerated and which ones are not. You should aim for three meals a day with one or more protein supplements as needed to reach your goal of 60 grams of protein daily. This stage encourages lean protein. Fruits, vegetables, whole grains, fat and sugar continue to be limited.

Tips For Beginning a Regular Diet: 

  • Avoid ?cheap calories? such as fats, high calorie liquids, sweets, ice cream, junk foods and cookies.
  • Remember, because the quantity of your intake is very small, it is crucial to eat highly nutritious foods.
  • Cut up each piece of meat to the size of an eraser on the end of a pencil.
  • Chew up each piece of meat individually, before swallowing.
  • Remember no liquids with meals!
  • High calorie liquids should be avoided. Consume only calorie free liquids.
  • Each meal should take an average of 30 minutes to consume. Eat slowly.
  • When in doubt about a new food, try it.
  • At least ½ of each meal should be high quality protein.
  • Quit when you are full. Do not challenge the capacity of your stomach pouch, to avoid stretching.
  • Do not smoke.
  • Do not use carbonated beverages, and avoid alcohol.

You may not feel hungry, so plan your meals by the clock to maintain adequate nutritional intake throughout the day. This will also make it easier to plan your fluid intake. Nutritional changes take place throughout the first year, and individual meal planning may be necessary with your dietitian.

Your goal is to lose fat, not lean body muscle or tissue. Good, quality protein consumption is extremely important. Protein has important functions:

  • It helps with healing.
  • Prevents break down of lean body mass.
  • Minimizes hair loss, and keeps skin, bones and nails healthy.
  • Helps with satiety. 

Your dietitian will always stress the importance of eating protein first. After surgery you will consume a smaller volume of food, because your pouch capacity is smaller. You will eat the protein portion of your meal first that way you know that before you are ?full?, you have fed our body what it needs to survive. Your surgeon will have specific guidelines as to the amount of protein you should be eating daily. It can range from 55-100 grams. 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. Approximately 75% of your weight is protein. Your body is made up of at least 10,000 different proteins. Protein substances make up muscles, tendons, glands, nails and hair. Growth, repair and maintenance of all cells depend on protein. The next section will explain to you the way in which our body gets proteins.

Amino Acids
Amino acids are the basic structural building blocks of proteins. Your body can produce 10 of the 20 amino acids your body needs to live. The other 10 are called essential amino acids because you can only obtain them by eating food. If you miss even one amino acid your body needs, your body won?t function properly. Your body does not store excess amino acids for later use as it does for fat and starch. Therefore, you must consume them everyday in the foods you eat. The following are two very popular amino acids that are always talked about when it comes to weight loss and maintenance.

Arginine - This is an essential amino acid that is important for growth and proper functioning of the immune system It is one of the three building blocks of creatine. It is needed for the formation of proteins such as collagen and elastin, and the vital substances such as hemoglobin, insulin and glucagons.

I mention this in particular because with the amount of weight that you are about to lose, you want your skin to look as healthy as it can. We have all heard of collagen and elastin in lotions that you may use. The following foods are rich in arginine which will help in forming these important proteins. Peanuts, cashew nuts, walnuts, piyal seeds, and most vegetables especially green and root vegetables. It also exists in a free state in garlic and ginseng. Remember to make sure that the foods you are eating are stage appropriate.

Glutamine - This is the most abundant amino acid found in muscles. It helps to build and maintain muscle tissue, helps prevent muscle wasting, increases brain function and mental activity, helps keep the digestive tract healthy, alleviates fatigue and depression, and decreases cravings for sugar and alcohol. You can understand the need for this amino acid with the intensity of your pending weight loss. Foods rich in glutamine are: beef, fish, poultry, eggs and dairy. Vegetarians can get glutamine by consuming legumes, hemp seeds, chia seeds, raw cabbage and beets. 

Vegetarianism and Protein 
Just to reassure those of you that are contemplating WLS and are practicing vegetarians of different degrees, it is easy for you to get quality protein too! Foods such as beans, grains, nuts, vegetables, beans, soy, tofu and tempeh are great examples. Plant based proteins also contain healthy fiber and complex carbohydrates. It is a great idea to consume many types of proteins because too much animal protein has been linked to formation of kidney stones and has been associated with colon and liver cancer.

Interesting fact: The human body can absorb 92% of protein found in meat and 91% of protein in soybeans. It is worth discussing the topic of soy for those of you that either do not know what it consists of, or are on the fence with the controversy surrounding it.

Soy - Soybeans contain natural isoflavones. Isoflavones are studied in relation to the relief of certain menopausal symptoms, cancer prevention, slowing or reversing of osteoporosis and reducing the risk of heart disease. These positives are talked about so often because they can potentially help a wide range of people. This article does not encourage or discourage the use of soy. It is purely informative in helping you to understand this topic and make an informed decision of your own.

Soy also has many negatives. Over 90% of soy is genetically modified and it also has one of the highest percent contamination by pesticides of any of the foods we eat. Soy can also block the body?s uptake of essential minerals like magnesium, calcium, iron and zinc. Soy can also block the uptake of enzymes which the body needs for protein digestion. This can cause gastric distress, reduce protein digestion, and cause problems with amino acid deficiencies. As previously mentioned- the best diet regimen is one that is varied and does not depend on one specific type of any food group as it?s main source. The jury is still out and research is ongoing in the soy matter. Stay tuned for further updates.

The following list was obtained from the U.S. Department of Agriculture?s National Database for Standard Reference, 2005 (8). It is very interesting to see the percentage of calories from protein for foods that we do not ordinarily think of containing protein. (Value per 100 grams of edible protein). 

Fruits   Legumes, Raw
Cantaloupe 10% Garbanzo beans 21%
Grapefruit 8% Kidney beans 58%
Peach 9% Navy beans 37%
Strawberry 8% Soybeans 35%
Tomato 19% Split peas 29%
Watermelon 8% Lentils 34%


Nuts and Seeds   Vegetables, Raw
Almonds 15%   Mushrooms 56%
Cashews 13%   Spinach 50%
Peanuts 18%   Watercress 84%
Pumpkin seeds 18%   Green peas 27%
Sesame seeds 12%   Broccoli 33%
Sunflower seeds 16%   Lettuce 36%
Walnuts (black) 15%   Zucchini 30%
Filberts 9%   Cauliflower 32%

Dumping Syndrome
Dumping syndrome happens in response to the presence of a high carbohydrate load entering into the intestine. After gastric bypass surgery, if you eat sweets it may sometimes be ?dumped? into the intestine instead of being released gradually, in small amounts.

Symptoms: Abdominal fullness, nausea, crampy abdominal pain followed by diarrhea within 15 minutes after eating. As a result, you may feel warm, dizzy, weak, faint, have an increased pulse rate, and break into a cold sweat.

Follow these four rules to help avoid dumping syndrome:

  1. Eat slowly
  2. Chew thoroughly
  3. Do not consume liquids with solids
  4. Avoid sugar


  • Your diet should be low in simple carbohydrates, low in fat, and high in protein.
  • All food and drink should be moderate in temperature. Cold drinks can cause gastric distress.
  • If ?dumping? is a problem, it may be helpful to lie down 20 to 30 minutes after meals, or even up to an hour.
  • Pectin, a dietary fiber found in fruits and vegetables, may be helpful. It delays gastric emptying, slows carbohydrate absorption, and reduces the glycemic response. (Consume fruits and vegetables according to Stages)
  • Read food labels and avoid foods high in added sugar. To identify sugar, look for ingredients ending in ose (example: dextrose, sucrose, and fructose). Other forms of sugar are corn syrup, honey, and molasses.
  • Sugar, or a form of sugar, listed in the first three ingredients on the ingredient list should be avoided.

Look for foods labeled sugar-free or no added sugar. Foods labeled dietetic, may not be sugar free.

Most surgeons require their patients take a vitamin/mineral supplement daily after surgery. It is recommended for the first 4-6 weeks post-op to take one in chewable form. Once your doctor advances you to a regular, solid consistency diet it is then okay to take it in pill form.

  • Calcium in the form of calcium citrate is also recommended daily. Your goal for calcium daily is 2,000 mg.
  • Daily recommendations for Vitamin D is 400 iu daily. This is usually obtained in your calcium supplement. Check your product?s label to see if both calcium and vitamin D needs are being met.
  • Additional supplementation such as iron, vitamin B12, folate, etc? depends on your surgeons protocols. It is common to take your lab work throughout the first year to determine if you are in need of additional vitamins and/or minerals. The need is determined on an individual basis. This is surgeon specific.
  • Interesting fact: Vitamins are best absorbed with food. Try to take them with meals. If vomiting occurs, take in between meals with liquids only. Do not take calcium and vitamins at the same time; calcium inhibits vitamin absorption.

Your Goal: 2Liters / Day 

Getting the right amount of fluid each day is essential to a healthy body. Water is especially important when the weather is very hot or very cold. In the summer, perspiring helps keep the body temperature within a normal range. In the winter, water acts as insulation. It is just as common to dehydrate in the winter as in the summer?don?t be deceived!

What is water?s job? Water transports nutrients and carries waste. It moistens your eyes, mouth, nose and hydrates skin. It ensure adequate blood volume, and acts as a main source of body fluids. Water protects against heat exhaustion and insulation in the cold. Water also helps carry medicines to the proper places in your body.

The Roux-en-Y gastric bypass partitions the stomach into two parts, with a very small ?pouch?. This tiny pouch can hold about 1 ounce, about the size of a shot glass. The small pouch makes it difficult to eat a large amount of solid food, but provides very little barrier to liquids when taken slowly.

Post-operatively, one of the main challenges for a gastric bypass patient over time is to maintain hydration. You will be allowed to drink 1-2 ounces of fluid at a time, however, 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.

What counts towards daily fluid? Anything that is non-carbonated, decaffeinated, calorie and sugar free. Using a liquid such as fruit juice or something that is high in calories, can lessen weight loss because of the caloric value. Fluids should be consumed regularly, but not during meals. The general recommendation is that you should stop drinking liquids once you have started your meal and to wait 30 minutes after you have completed your meal to resume drinking. This will ensure absorption of the nutrients you have just eaten. If you drink during your meal you will tend to wash the food out of the stomach pouch, and consume more food than is desirable. This will make it more difficult to lose weight and retain nutrients.

Suggestion: Eat your meals without liquids on the table. This will make it easier for you not to feel tempted!

Fluid needs will continue to change throughout the first year after surgery. To optimize weight loss and reach your daily fluid goals, follow up with your dietitian routinely.

Signs of Dehydration:

Percent Loss of Body Water Effects of Dehydration
0-1% Thirst
2-5% Dry mouth, headache, fatigue
6% Increase in body temperature, pulse, dizziness, weakness
8% Dizziness, increased weakness
10% Muscle spasms, swollen tongue, delirium
11% Kidney failure, poor blood circulation

 You can see how quick and intense dehydration can happen. Do your best to monitor your daily fluid intake. If you have problems getting in your requirements, let your dietitian and doctor know.

Remember, beverages with caffeine do not count towards meeting daily fluid intake. 

Nutritional Lab Values
Throughout the first year, your surgeon will be taking blood work to better help her/him assess your health status. Nutritionally, we look at the following labs to evaluate you for potentially developing deficiencies. This is common due to the smaller volume of food that you are consuming. Lab work is interpretive and should be discussed with you so you can understand your health.

Lab Value Normal Range
Albumin 3.5 - 5 g/dl
Calcium 8.8 - 10.3 mg/dl





120 - 199 mg/dl

30 - 70 mg/dl

65-180 mg/dl

0 - 200 mg/d

Folate 3.6 - 20 ng/dl
Glucose 70 - 115 mg/dl
Iron 65 - 150 mcg/dl
Potassium 3.5 - 5.3 mEq/l
Prealbumin 19 - 43 mg/dl
Vitamin B12 >300 pg/ml

(Ranges may vary by lab)

Get Specific with Nutritional Meanings 
The following definitions are here to help you make smarter food selections for you and your family. An informed shopper is a smart shopper. Don?t be fooled by fancy packaging or claims that are not founded. 

Sodium free  5 mg or less per serving
Low sodium  140 mg or less per serving
Very low sodium 35 mg or less per serving 
Reduced sodium 1 serving has no more than 75% of the sodium in the regular product
No salt added  No salt added during processing
Fat free  Less than 0.5 grams of fat per serving
Saturated fat free  Less than 0.5 grams per serving and the level of trans fatty acids does not exceed 1% of total fat
Low fat (3 grams or less per serving)
Low saturated fat  1 gram or less per serving
Reduced or less fat  at least 25% or less per serving than the regular product
Cholesterol free Less than 2 mg of cholesterol and 2 grams or less of saturated fat per serving
Low cholesterol 20 mg or less and 2 grams or less of saturated fat per serving
High fiber  5 grams or more per serving
Good source of fiber  2.5 grams to 4.9 grams per serving
More or added fiber  at least 2.5 grams or more per serving than the regular product
Sugar free  less than 0.5 grams per serving

Sugar Alcohols
Sugar alcohols: Sorbitol, mannitol, erythritol, inulin, HSH (hydrolyzed starch hydrolysate), xylitol, lactitol, maltitol, galactitol, inositol, ribitol, dithioerythritol, dithiothreitol, and glycerol.

Sugar alcohols, also known as polyols, are ingredients used as sweeteners and bulking agents. They occur naturally in food and come from plant products such as fruits or berries. Sugar alcohols are a carbohydrate with a chemical structure that partially resembles alcohol and sugar. There is no ethanol in them so they are not an alcohol. Many foods labeled "sugar-free" contain sugar alcohols. They offer fewer calories (1/2 to 1/3 less) than regular sugar. There is less than 1.0 gram of CHO per 1 gram of sugar alcohol. Sugar alcohols = 2.6 calories per gram. So, the are NOT considered a "free food".

Sugar alcohols are appropriate for a bariatric and/or diabetic patient to use. Blood sugar does have the potential to rise, but is much slower than ingesting a true sugar. It is important to keep in mind that we are all individuals, and our bodies will react differently to these products.

Potential Problems:

Consuming more than 50 grams of sugar alcohols a day can induce diarrhea, gas, and/or bloating. Sugar alcohols are incompletely absorbed from the small intestine into the blood. Over consumption may produce a laxative effect.

Sugar alcohols may act as "trigger foods" causing carbohydrate cravings or binges.

Sharon George received her B.A. in Psychology from Syracuse University. She completed a second Bachelor?s degree in Nutrition at L.I.U. C.W. Post. She later went on to receive her Master?s degree, with honors, in Community Counseling from Hofstra University. Sharon has worked as a clinical Registered Dietician at Mercy Medical Center, St. Francis Hospital, and Winthrop University Hospital. She has been published in both OH Magazine and Bariatrics Today and has guest lectured at The American Heart Association?s National Annual Convention. Sharon is affiliated with the following organizations:

ADA ? American Dietetic Association
LIDA ? Long Island Dietetic Association
ASBS ? American Society for Bariatric Surgeons

This information has been provided courtesy of the New York Bariatric Group. Please visit the New York Bariatric Group at


Most Active
Recent Topics
Stacy8888fan · 0 replies · 13 views
Bowel problems
Stacy8888fan · 1 replies · 66 views
Poll - Regain - 50%
Mentor · 3 replies · 327 views
13 years out and questions
Musicmama88 · 3 replies · 319 views