How Much Food Can You Really Eat After a Gastric Bypass?

Portion sizes need to be noticeably smaller after gastric bypass surgery.
Image Credit: Luis Alvarez/DigitalVision/GettyImages

If your weight poses a considerable threat to your health, and dietary changes and exercise haven't helped, your doctor may bring up the possibility of gastric bypass surgery. It's one of the most common types of weight loss (aka bariatric) surgery in the United States, and is generally considered the least prone to complications, according to the Mayo Clinic.

Here, we'll dig into what the surgery entails and how it will change your eating habits, including how much food you can eat per sitting after a gastric bypass.


About Gastric Bypass Surgery

Gastric bypass surgery induces weight loss via two surgical changes to the digestive tract. The surgeon creates a small pouch at the top of your stomach, separate from the rest of your stomach. Additionally, food in the pouch is re-routed so that it bypasses (hence the name of this procedure) most of your stomach and the first part of your small intestine.

Read more: The Long-Term Effects of Obesity on Health

The procedure causes weight loss in two ways, explains Melissa Schuster, RDN, CDN, a bariatric dietitian based in New York City. "The new stomach pouch is very small, only holding about one ounce, which limits the amount of food and calories you can consume. 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."


After your surgery is completed, your doctor will give you a diet to follow, indicating what kinds of food, and in what amounts, you can have at each meal. The long-term success of the procedure depends in large part on how well you adhere to the post-surgical diet guidelines. These will change as your recovery progresses.

The Liquid-Only Phase

So, how much can you eat per sitting after gastric bypass surgery? That depends which phase of recovery you're in.


For one to two days after your surgery, you can't eat anything at all to give your digestive track some healing time. After that, you'll be put on a clear-liquid-only diet (clear broth or apple juice, for instance). Follow your doctors instructions about how much and how often. You will need to measure out the liquids to be sure you're not consuming too much.

After a few days, in the absence of nausea or any other digestive issues, your doctor might allow full liquids, like strained soups, gelatin and milk. The amounts and increments will likely be the same; the difference is that the liquids no longer have to be clear.


Pureed, Soft Foods Are Next

Your surgeon will let you know when you can move on to pureed and soft foods. You'll start with food that is the consistency of "stage one" baby food. (You can eat actual baby food if you find that easier than pureeing your own.) You should start each meal with protein, like finely ground fish or moist poultry, and then some pureed vegetables or fruit, such as applesauce.

Protein is key to proper healing. When your doctor OKs soft foods, you can enjoy scrambled eggs, yogurt, mashed potatoes and the like. This phase usually lasts about two to four weeks, but it depends on how fast your body is healing and adjusting to your changing eating patterns.

Read more: How to Stay Positive Through Every Stage of Your Weight-Loss Journey

Your Lifelong Eating Plan

Your doctor may give you a list of foods, particularly high-fiber ones, that should be avoided or limited. Dry foods like stringy red meat and chicken breast can also prove problematic, notes Schuster, as they can feel "stuck" after you swallow, especially if not chewed until smooth. In general, you'll need to get used to taking smaller bites and chewing your food slowly and thoroughly.

But beyond that, once you get the green light from your doctor, you can finally eat regular food, though not in pre-surgery amounts. Your reduced-size stomach will never be able to hold more than one cup of chewed food per meal (as opposed to about four cups before you had gastric bypass surgery). Using that math, you'll be able to consume about a quarter of the food you did pre-surgery at each meal.

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

For example, a typical dinner might be a 3-ounce boneless chicken thigh and one quarter cup of steamed broccoli. Breakfast might consist of one quarter of a banana and one scrambled egg.

"Whole grains can be part of a healthy diet, but should only be introduced once the patient's weight stabilizes and hunger increases, and only if the patient is meeting recommendations for protein, fruit and vegetable intake," Schuster tells

It is crucial that you learn to recognize when you are full, and to respect those signals. You should stop eating just as soon as you feel full and never stuff yourself — not even on Thanksgiving! "It is important to eat slowly and mindfully," says Schuster.

During any stage of recovery after a gastric bypass, you should not chew gum, which can cause a blockage if accidentally swallowed and introduces air into your stomach (as do carbonated beverages and sipping through a straw, which are also to be avoided). You'll also need to break the habit of drinking with meals. Wait at least a half hour after eating to drink, urges the U.S. National Library of Medicine. And when you do drink, sip slowly, never gulp.