How Many Calories Should You Eat After Weight-Loss Surgery?

Small portions of high-protein foods like tuna are a nutritious part of your long-term diet after bariatric surgery.
Image Credit: Julie Deshaies/iStock/GettyImages

It's important to follow a special diet after weight-loss surgery to help your body recover and to give the procedure the best shot at success. And understanding how much you can eat after gastric bypass and other weight-loss procedures will help your post-surgery diet go more smoothly.

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There are several types of weight-loss surgeries (also known as bariatric surgeries), all of which alter your digestive system to help you lose weight, according to the Mayo Clinic. The most common bariatric procedures include gastric bypass and sleeve gastrectomies.

Gastric bypass surgery induces weight loss via two surgical changes to the digestive tract. First, the surgeon uses staples to section off a small upper pouch in your stomach, which is where the food you eat will go, per the U.S. National Library of Medicine (NLM). Then they'll connect this pouch to your small intestine.

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​The procedure causes weight loss in two ways: "The new stomach pouch is very small, only holding about one ounce, which limits the amount of food and calories you can consume," says Melissa Schuster, RDN, CDN, a bariatric dietitian in New York City. "There is also a mechanism of malabsorption. Because part of the small intestine is bypassed, you do not absorb as many calories or nutrients from what you are eating."

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A gastric sleeve procedure, on the other hand, removes an oblong portion of your stomach so that you have a smaller stomach overall, according to the Mayo Clinic.

Below, learn how many calories you can eat after gastric bypass or gastric sleeve surgery, depending on your phase of recovery.

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Tip

How much you can eat after gastric bypass or gastric sleeve surgery may vary based on your circumstances, so make sure to follow your doctor's instructions about what, how much and when to eat, per the Mayo Clinic.

Right After Surgery

For the first day or so after your surgery, you'll skip eating and only drink water to give your digestive tract some time to heal, according to Tufts Medical Center.

After that, you'll follow a clear liquid diet for another day or two to continue to go easy on your digestive system. At this point, your calorie intake and portion sizes will be very small (likely less than 300 calories per day), according to UCSF Health.

Foods you can eat on a clear liquid diet include:

  • Sugar-free electrolyte sports drinks
  • Clear, sugar-free sodas like ginger ale
  • Tea or coffee (without milk or cream)
  • Clear soups and broths like vegetable, beef and chicken broth or bouillon

How Big Is Your Stomach After Gastric Bypass?

This procedure makes your stomach the size of a golf ball, which means you can eat about 1 ounce at a time after gastric bypass surgery, per Penn Medicine.

Similarly, how much food can a gastric sleeve hold? About 3 or 4 ounces, according to Penn Medicine.

A Few Days After Surgery

You'll typically progress to a high-protein liquid diet a few days after your procedure and stick to it for about two weeks (though this timeline may vary based on how long it takes your body to recover), according to UCSF Health. During this phase, you'll drink no more than 400 calories a day in the form of high-protein, thick liquids that are low in fat and sugar.

You'll also stick to small portion sizes after your gastric bypass or gastric sleeve procedure so your stomach is able to empty more easily and so you can disperse your calories throughout the day. Stick to 1-tablespoon portions of food and 1/4-cup portions of liquids, slowly increasing to 2-tablespoon and 1/2-cup servings as your body adjusts, per UCSF Health.

According to Tufts Medical Center, adults should aim to get the following amounts of protein during this phase of recovery:

  • People assigned female at birth (AFAB):​ 50 to 60 g
  • People assigned male at birth or people AFAB who are taller than 5 feet and 8 inches:​ 60 to 70 g

Per UCSF Health, good sources of protein on a liquid diet include:

  • Skim or 1% milk (as long as you aren't lactose intolerant)
  • Lactose-free or soy-based low-calorie drinks
  • Sugar-free pudding
  • Sugar-free, nonfat yogurt
  • Low-fat cottage cheese
  • Broth-based or other low-fat soups
  • Refined hot cereals that are low in fiber, like cream of rice or cream of wheat
  • High-protein, low-calorie liquid supplement drinks
  • Protein powder mixed into fluids like milk or water

How Many Ounces Can You Drink After Gastric Bypass or Gastric Sleeve Surgery?

It's important to stay well-hydrated throughout this and other phases of your recovery. Drink at least 64 ounces of water per day, according to Tufts Medical Center, and sip fluids separately from your meals (by about 30 minutes).

Two Weeks After Surgery

You can typically start to incorporate puréed and soft foods into your diet about two weeks after your gastric bypass or other bariatric surgery, according to UCSF Health.

During this phase, you'll eat no more than 500 calories a day, divided amongst six to eight meals (that's about 70 calories per meal). Your meal sizes should be about 1/4 cup for food and 1/2 cup for liquid.

Per UCSF Health, soft foods you can add to your diet may include:

  • Yogurt
  • Cottage cheese
  • Well-cooked, puréed vegetables
  • Mashed potatoes
  • Applesauce
  • Canned fruit
  • Hot cereals
  • Noodles
  • Scrambled egg whites
  • Canned tuna
  • Lean fish like cod or halibut
  • Tofu
  • Lean ground meats or poultry

Try new foods slowly and only continue eating those that you tolerate well. To help your body adjust, chew thoroughly and don't take more than two bites of a new food every 20 minutes, according to UCSF Health.

Tip

Stop eating when you feel satisfied to avoid stretching out your stomach, according to the NLM.

Two Months After Surgery

You can start to include more solid foods and calories into your gastric bypass diet after about two months, according to UCSF Health. You may be in this phase for as long as several months while your body continues to heal.

You'll up your daily caloric intake to about 900 to 1,000 calories divided amongst three small meals and four or five snacks (that's roughly 150 to 250 calories per meal and 50 to 100 calories per snack). Keep eating serving sizes of 1/4 cup for food and 1/2 cup for liquid.

At this point, it's also best to get most of your nutrients from food, rather than supplement drinks, per UCSF Health. Aim to eat this amount of different food groups every day:

  • 3 servings of nonfat and low-fat dairy products like milk and yogurt
  • 3 servings of lean and low-fat meat or meat alternatives like tofu
  • 3 servings of starchy foods like potatoes or squash
  • 2 servings of cooked vegetables
  • 1 serving of skinless fruit

How Many Grams of Fat Can You Eat Per Day After Gastric Bypass?

It's best to stick to a low-fat diet after any bariatric surgery because the procedure can make it harder to digest and absorb fat, per Johns Hopkins Medicine. Avoid eating more than 5 grams of fat per meal, according to Tufts Medical Center.

Maintenance Diet

Between two and six months after surgery, you'll transition into your lifelong maintenance diet to keep losing weight and maintaining weight loss. How many calories and what you should eat in the long term after a gastric bypass or gastric sleeve procedure varies depending on your nutritional needs, so work with your doctor or dietitian to come up with the best diet plan for you, per Tufts Medical Center.

Generally, though, your daily calorie intake during the maintenance stage is between 1,300 and 1,500 calories, according to the University of Rochester Medical Center. You'll typically eat about 1 to 1 1/4 cups of food per meal, for a total of about three meals and two snacks each day (that's roughly 250 to 350 calories per meal and 100 to 150 calories per snack).

But the exact amount of food eaten at this stage should be based on hunger and satiety levels, Schuster says. Further, meals should prioritize protein and vegetables or fruit, and limit high-sugar and high-fat foods.

And even though you'll be back to eating a variety of foods one year after your gastric bypass or gastric sleeve procedure, you'll continue to eat smaller portions given your stomach's new, reduced size — in fact, pushing your body to eat larger servings could damage the surgical site.

In this phase, a typical dinner might be a 3-ounce boneless chicken thigh and 1/4 cup of steamed broccoli. Breakfast might consist of a 1/4 of a banana and a scrambled egg.

How to Get Food Unstuck After Gastric Bypass

Your doctor may recommend you limit or avoid high-fiber foods like beans or dry foods like stringy red meat and chicken breast, Schuster says, as they can feel "stuck" after you swallow, especially if not chewed until smooth.

To avoid this, take small bites and chew your food slowly and thoroughly.

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