What is Bariatric Diet?

Bariatric diet allowed food
Allowed food for bariatric dietary plan

The bariatric diet is a specific eating plan prescribed by your surgeon or dietitian to help you to lose weight before and after bariatric surgery. The nutritional guidelines focus on high-protein, low-carbohydrate and sugar-free food and beverage.

In short, the bariatric diet requires you:

  • Starting the low-carb, high-protein diet 2 weeks before surgery;
  • Eating the approved food and liquids starting from the protein shakes;
  • Avoid fat food, sugar beverage, high calorie snacks, coffee and alcohol;
  • Losing 15 to 20 pounds and shrinking your liver to make surgery safer;
  • Not cheating on the bariatric diet especially right before the operation;
  • Eating smaller portions but often during the day to better deal with hunger;
  • Drinking at least 64oz of sugar-free liquids a day but away from meals;
  • Following 4 bariatric diet stages: clear liquid, full liquid, soft and solid food;
  • Do not forget your post weight-loss surgery vitamins and supplements.

As soon as you reach your ideal weight, your dietitian will change the diet once again to help you to maintain the achieved result as long as possible.

Bariatric diet before surgery

Why should you lose some pounds before weight loss surgery? Obese people have larger liver due to the excess fat stored in the abdominal region, in and all around the liver.

Even if the laparoscopic procedure is minimal invasive, during the surgery, the bariatric surgeon has to move apart the liver. If that organ is too large complications may occur.

In order to lower any risk, your dietitian will prescribe you a specific bariatric diet before surgery high in protein and based on liquid food. Usually the pre-op diet allows you to consume up to 1200 calories a day.

Main reasons for losing weight before bariatric surgery are:

  1. Treating nutrient or micronutrients deficiencies before to undergo the bariatric surgical procedure (especially: iron, vitamin B12 and vitamin D);
  2. Cutting risks associated with the surgical treatment and general anesthesia;
  3. Reducing operating time;
  4. Minimize post-op complications;
  5. Promoting fast recovery and proper healing;
  6. Preparing the patient for after-surgery bariatric diet and post-op lifestyle.

Bariatric diet after surgery

Immediately after the weight loss surgery procedure and for the rest of patient’s life it is very important to follow a new lifestyle starting from eating habits. Your surgeon, dietician and psychologist will support you to start and go through five-phase post-bariatric surgery diet plan.

Please remember that:
1 fluid ounces (fl. Oz.) is equal to 0.029 Liters;
1 ounce (oz) is equal to 28.34 grams (g);
1 cup = 8 fl. oz. = 250 ml.

Phase 1: Bariatric clear liquid diet

The stage 1 lasts 15 days (weeks 1 and 2) and starts immediately after the weight loss surgery while the patient is still in the hospital. Because patients can drink clear fluids only, the phase 1 is also called bariatric liquid diet.

Phase 1 allowed fluids and beverages in bariatric liquid diet:

  1. Clear broths made with chicken, vegetables or beef;
  2. Fruit juices (without pulp) diluted with water (50% juice + 50% water);
  3. Sugar-free flavored drinks (such as those for sport);
  4. Caffeine-free beverages such as tea or coffee without any type of sugar or cream. Caffeine may cause acid reflux.
  5. Crystal Light;
  6. Popsicles;

Eating tips during bariatric liquid diet:

Do not drink carbonated beverages. Carbonated drinks, in fact, introduce air into the stomach causing gas and bloating;
For the reason explained above, do not use straws.

The most important thing, at this first stage, is that you stay hydrated. To ensure you the right hydration, your doctor or registered dietitian will suggest you to drink 48 to 64 ounces (fl. oz) of fluids per day (1.5 to 2 liters).

The best way to assume fluids is drinking small sips throughout the whole day.

Do not worry if you cannot reach immediately the indicated quantity of liquid. Day by day you’ll be able to increase the amount of liquids your new stomach can tolerate.

Phase 2A: Bariatric full-liquid diet and Protein Shakes

high protein shake example
High protein shake

The last of the second stage of bariatric diet depends on the specific weight loss surgery performed: Gastric Bypass or gastric sleeve (Roux-en-Y).

Phase 2 is the stage where liquid proteins come into bariatric diet. We all know that traditional food is the best source of protein, vitamins and minerals. However, at phase 2 bariatric diet your stomach is still healing from surgery, that’s why it cannot digest that solid food yet.

It is in the phase 2A that your doctor will add liquid protein supplements to your bariatric diet plan.

Phase 2 allowed foods in bariatric full-liquid diet:

  1. Everything listed in phase 1 bariatric clear liquid diet;
  2. Protein powder shakes with at least 18 grams of protein per serving (8 to 10 ounces);
  3. 0% fat plain Greek yogurt (Such as: Chobani or Dannon light Greek yogurt that provides 80 calories, 12 grams of protein and 5 to 8 grams of sugar);
  4. Low-fat (1%) or, better, skim milk (0.1% fat). Skim dry milk is allowed too;
  5. Sugar-free ice cream and sorbet;
  6. Fruit juices (without pulp’s pieces) diluted with water or skimmed milk (50% juice + 50% water/milk);
  7. Bariatric high protein meal replacement (Best brands on the market: BariatricFusion, BariatricPal, BariatricAdvantage – sold even by Amazon online store). Meal replacement are available in different flavors: chocolate, strawberry, vanilla, banana etc. Unflavored high protein meal replacement can be mixed with milk, plain water, soup or yogurt.
  8. Instant breakfast drinks (i.e. BariatricChoice High Protein Drink or Carnation Instant Breakfast).

Eating tips during bariatric full-liquid diet:

  • Sip 1 ounce of liquid over 15 minutes (1/3 cup);
  • All drugs, supplements and vitamins should be liquid, crushable, or chewable;
  • Your bariatric protein shake should contain 15 to 20 grams of protein and less than 200 calories per serving;
  • To prevent nutrient deficiencies, your dietitian will prescribe you multivitamin (you should take it twice a day), iron and calcium citrate supplement (chewable or liquid form);
  • At this stage, the daily caloric intake for gastric sleeve and gastric bypass patients should be about 400 calories.
  • The daily protein intake for duodenal switch patients is higher, about 100 grams/ day;

Phase 2B: Bariatric pureed diet

The second part of stage 2 also lasts 15 days (weeks 3 and 4).
Finally it is time to add pureed food to your menu. It is very important that the allowed food has the consistency of baby food (homogenized), without any solid pieces of pulp, seeds or skin.

Phase 2B allowed foods in bariatric pureed diet:

  1. Everything listed in phase 1 and phase 2A (bariatric clear liquid and full liquid diet);
  2. Strained cream soups (potato, mushroom, beans, chickpeas or peas);
  3. Filtered rice cream;
  4. Boiled or scrambled eggs;
  5. Pureed meats: beef, chicken, turkey (¼ cup broth with ¼ cup mashed meat);
  6. Pureed white fish fillet (Atlantic Cod, Sole, Flounder, Sea Bass, haddock);
  7. Boiled potatoes and/or carrots mashed using a fork;
  8. Pureed vegetables: spinach, carrots, summer squash or green beans (¼ cup vegetable with broth or water);
  9. Light cottage cheese;
  10. Tofu cheese;
  11. Fresh ricotta cheese;
  12. Baby food (homogenized meat);
  13. Baby oatmeal;
  14. Pureed fruits: peaches, bananas, apricots, pears, pineapples, melons and mango pulp (¼ cup mashed fruit and plain water);
  15. Sugar-free applesauce;
  16. Tomato juice (caution: it may cause heartburn);
  17. Skimmed milk and powder protein shake;
  18. Bariatric high protein meal replacement;
  19. Protein supplements added to food or melted in water.

Eating tips for bariatric pureed diet:

  • At this stage, the daily caloric intake is around 500 calories a day;
  • Each weight loss patient should eat four to eight very small meals a day;
  • The portion size should be equal to one quarter cup for mashed food and half cup for liquids (too much food entering your new small stomach may cause dumping syndrome);
  • Add one new type of pureed food at a time to check the tolerance.

Phase 3: Bariatric Soft diet

The phase 3 lasts 60 days (months 2 and 3). Adding soft food (easy-to-chew) to your diet plan after bariatric surgery is the first step to go back to eat normally.

Phase 3 allowed foods in bariatric soft diet

  1. All food in phase 1, phase 2A and phase 2B;
  2. Bean soup or rise cream;
  3. Mashed hot cereals;
  4. Egg: poached, soft-boiled or soft-scrambled (preferably egg whites);
  5. Lean ground meat: chicken, turkey, beef or pork (finely chopped);
  6. Cooked, pureed white fish, all varieties: (i.e. baked cod, sole fillets);
  7. Cottage cheese or Non-fat cheese like ricotta and tofu;
  8. Well-cooked vegetables like squash, green beans or lentils;
  9. Boiled carrots and or sweet potatoes without skin;
  10. Soft fresh fruit, without seeds or skin: mashed bananas or mango, cucumbers, peaches, pears or avocados;
  11. Canned fruit in own juice;
  12. Baby food: homogenized meat, fruits or vegetables;
  13. Bariatric protein shakes;
  14. Supplements: Multivitamins, Calcium, Vitamin D, Vitamin B12, folic acid or iron supplement.

Bariatric soft diet eating tips

  • 800 to 1000 calories per day is the maximum allowed in Phase 3 diet after bariatric surgery (gastric sleeve as well as gastric bypass patients);
  • At this stage, your stomach should be able to handle solid foods so you can consume three to six meals per day;
  • In order to avoid dumping syndrome, eat slowly, do small bites and chew food thoroughly;
  • Eat food high in protein first, vegetables second and carbohydrates third;
  • Do not drink liquids while eating. Wait at least 30 minutes before or after each meal;
  • Continue to take daily multivitamin and mineral supplements;
  • Do not forget bariatric protein shakes between meals in order to meet your daily protein requirement (60 to 80 grams).

Phase 4: bariatric stabilization diet

The stabilization phase begins at month 4 and lasts for the rest of the patient’s life (long-life).

Phase 4 allowed foods in bariatric stabilization diet

  1. All food listed in the previous stages;
  2. Soups with finely ground meat (poultry, beef, turkey, chicken);
  3. Hard boiled eggs;
  4. Hot cereals;
  5. Non-fat breakfast cereals softened in skim milk (0.1% fat) or Greek yogurt;
  6. All varieties of fish (shellfish included);
  7. All varieties of cooked vegetables;
  8. Sliced or grated low fat cheese such as ricotta, tofu (2g of fat and 0g of saturated fat) and feta (Greek cheese made in the U.S. with cow’s milk);

Eating tips for bariatric stabilization diet:

  • In the stabilization period your diet after bariatric surgery allows you 900 to 1000 calories (in some cases up to 1200 calories);
  • The amount of daily protein is the same as in the previous stage: 60 to 80 grams. A balanced mix of natural food and bariatric protein shakes help the patient to reach the goal;
  • Your stomach is ready to go back to three meals a day eating protein sources first;
  • As soon as you feel satisfied, you should stop eating;
  • Be sure to stay hydrated drinking 48 to 64 ounces of fluids throughout the day;
  • Stop drinking 30 min before eating and 30 min after.


Before and after bariatric surgery, it’s very important you strictly adhere to the eating plan your dietitian provides you. Following the 5 stages dietary guidelines will help your body to recover faster, to lose the excess weight quickly and avoid to re-gain weight in the future.

Exercise is also a crucial element of your journey towards a healthy way of eating. Most multidisciplinary equips involve personal trainer to provide patients with customized work out. Many doctors encourage their patients to start walking a few minutes each day as soon as you return home.

External Resources

American Society for Metabolic and Bariatric Surgery: ASMBS
American Dietetic Association: ADA