Your diet will change after weight loss surgery — here’s how to do it

Story by: Sara Thompson on December 1, 2022

Lots of things change after bariatric surgery (also called weight loss surgery or WLS), but perhaps one of the most important is your diet. After bariatric surgery such as the gastric bypass, what, when and how you eat are crucial to your long-term success.

What to eat before and after bariatric surgery

Pre-surgery diet

Before bariatric surgery, your doctor might ask you to eat in a specific way to lose some weight — anywhere from 5 pounds to a percentage of your body weight, depending on how heavy you are.

“We want to give you the best shot at success,” said Benjamin D. Tanner, M.D., general and bariatric surgeon with Norton Weight Management Services. “This type of diet before is close to what patients will be consuming after surgery in order to ensure lifelong success anyway, so starting it before surgery only helps develop habits that can continue after surgery.”

Phase 1

For the first few weeks after surgery, you will be on a liquid diet. Fluids such as broth, water and sugar-free Popsicles or gelatin to start with, then after 24 hours, you can add in protein shakes. This continues for about two weeks.

Phase 2

At two weeks post-surgery, you will introduce soft foods including purees, hummus, scrambled eggs and finely chopped meats such as chicken. You still will supplement with protein shakes, and aim to get protein and other nutrients from food as much as possible. At five to six weeks post-surgery, you will slowly integrate tougher textures such as soft fruit and cooked soft vegetables, as well as some grains. This phase lasts through week four.

Phase 3

At five weeks after bariatric surgery, you will be able to eat what will become your “regular” diet. You still will emphasize protein at each meal, include vegetables and supplement as needed.

“There are some foods you might need to reduce or eliminate, based on how your body responds to them,” Dr. Tanner said. “Those include carbonated drinks, spicy food and caffeine. High-sugar and highly processed foods will be greatly reduced as well.”

At this point, you will be able to recognize when you feel full after eating. It will be different from before surgery, and even from the first two phases.

Complications after bariatric surgery

Many patients report experiencing at least mild symptoms of one or more of the following after bariatric surgery.

• Dumping syndrome: Though uncommon, dumping syndrome is when the stomach empties food into the small intestine faster than normal, causing symptoms such as nausea, abdominal cramping and diarrhea. It is caused by eating too much sugar.
• Constipation: Decreased or lack of physical activity, lack of fiber and dehydration contribute to constipation.
• Dehydration: Hydration changes drastically after bariatric surgery. You should not drink fluids with meals and instead should consume about 64 ounces (about 1.9 liters) of mostly water throughout the day.
• Weight gain or failure to lose weight: If you gain weight or don’t lose any weight, talk to your doctor.

“The most successful patients have a combination of tools,” Dr. Tanner said. “They follow the nutrition plan, they pay attention to their bodies’ hunger and satiety [fullness] cues and they have the right mindset. If you haven’t done the mental work, it’s going to be much harder for you.”

Dr. Tanner encourages bariatric surgery patients to have a solid emotional and social support system, as well as a change in their lifestyle to include more activity.

Norton Weight Management Services is recognized for superior care by the American College of Surgeons and the American Society for Metabolic and Bariatric Surgery. Norton Women’s & Children’s Hospital is designated as a Blue Distinction Center+ by Anthem for expertise and efficiency in bariatric surgery. These designations may be a requirement of your health insurance plan.