After Weight Loss Surgery: The First 30 Days

Medically Reviewed By William C. Lloyd III, MD, FACS

Weight loss surgery (bariatric surgery) is a life-changing procedure. It isn’t a quick fix, but the results can be dramatic. In the long-term, people can lose up to 60% of their excess body weight. Success depends on initial BMI (body mass index), the type of surgery, and how well people stick with the lifestyle changes. Typically, results peak one year after surgery. But the changes right after surgery can be intense. Here’s what to expect during the first 30 days after bariatric surgery.


Diet is an area of drastic change after weight loss surgery. Nutritional goals include getting enough protein to keep your muscle mass, staying hydrated, and using vitamin and mineral supplements.

For most of the first 30 days, bariatric surgery patients eat a liquid diet. This transitions to a soft-food diet 2 to 3 weeks after surgery. Protein drinks and shakes will help maintain muscle mass. Nutritionally complete protein drinks or liquid supplements will provide vitamins and minerals. You will only be able to consume 1 to 2 ounces at a time. As a result, the intervals between meals are short. 

Frequent fluids are also necessary. In order to avoid dehydration, people need 6 to 8 cups of fluid each day. This means you may need to drink small amounts of fluids several times an hour to stay hydrated. Maintaining this schedule of frequent fluids and liquid meals can be a challenge. It may be helpful to write out the plan for your day. Downloadable smartphone apps like ‘Daily Water’ can help you stay hydrated.

Weight Loss

Weight loss is one of the goals of bariatric surgery. The amount of weight loss will depend on the person and the procedure. But it tends to be rapid in the first few months. During the first 30 days after bariatric surgery, the average weight loss is 5 to 15 pounds per week. Men tend to lose weight at a faster pace than women. By two months, most people average a 20% loss of excess weight.


Weight loss surgery changes how you can take medicines and which medicines you need. It also changes the way the body absorbs some drugs. As a result, extended-release, delayed-release, and enteric-coated medicines may not work well after bariatric surgery. Immediate-release forms of drugs tend to work better.

You will need to take vitamin and mineral supplements for your lifetime. You will also need to avoid aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) unless your doctor says otherwise. Doctors usually prescribe an acid-blocking drug for the first few months after weight loss surgery. Some people continue this drug if they must take aspirin for a heart or blood condition.

Doctors also use ursodiol (Actigall) to prevent gallstones after weight loss surgery. This is a frequent complication that occurs in up to 50% of bariatric surgery patients.

On the other hand, weight loss surgery may improve many obesity-related conditions, such as diabetes. You may find that you no longer need medicines to control symptoms or diseases you had before surgery. Talk to your doctor before stopping any of your medicines.

Obesity-Related Conditions

Reducing the risk of obesity-related conditions is another goal of weight loss surgery. Here again, the results can be rapid and dramatic. High blood pressure, diabetes, and GERD (gastroesophageal reflux disease) often improve within days of bariatric surgery. 

In the first 30 days after surgery, it’s important to monitor blood sugars daily. They often return to normal quickly. In fact, most people are able to completely stop blood pressure and diabetes medications soon after surgery. This can happen even before weight loss.


There can be some problems in the first 30 days after weight loss surgery. Constipation is common shortly after surgery. It’s usually due to pain medicines and dehydration. Keeping up your fluid intake will help. Wound infections can also be a problem, especially with a large incision from open surgery. Call your doctor right away if you have fever or pain, redness and discharge from your wound.

Vomiting may occur a few times a week. Often, it feels like food gets stuck and you must regurgitate it. During the first 30 days, this may mean that you’ve eaten too much. Talk to your doctor to be sure you are eating or drinking the right amount of food. You may need to weigh your food on a food scale to confirm you are eating the correctly-sized portions.

You should also call your doctor if you have persistent vomiting; your vomit is bloody or looks like coffee grounds; you have dark, tarry stools; or you feel faint or lightheaded. These are signs of possible complications, including internal bleeding from your stomach or intestines. Your doctor may recommend an endoscopy to check your stomach.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Sep 11
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