Diet After Bariatric Surgery

Weight loss surgery involves reducing the capacity of the stomach to hold food, and therefore the amount of calories and nutrients that can be absorbed in the intestines. A patient’s diet needs to be modified accordingly after surgery to ensure maximum nutrition while reducing calorie intake.

A typical diet plan for a patient who has undergone bariatric surgery involves:

  • The stage 1 diet that is provided at hospital immediately after surgery. This initial diet comprises mainly liquids that the patient can slowly sip until the new stomach or stomach pouch is full.
  • The stage 2 diet is made up of low-sugar, liquid or semi-liquid foods such as warmed cereal with milk.
  • The stage 3 diet is designed for when a patient is discharged from hospital and includes semi-solid, pureed, and finally soft foods. The progress to soft food is slow to allow time for post-operative wounds in the stomach and intestines to heal.

Diet progression

Initial requirements include enough liquid to prevent dehydration and sufficient protein. Later, the diet needs to be adjusted to accommodate nutritional needs. The size of the stomach pouch is about one ounce and initially, as little as two to three teaspoons of food may make the patient feel full. Over time, the pouch stretches bit-by-bit to allow more food intake.

The diet’s composition

About three quarters of the patient’s calorie intake should come from protein sources such as eggs, fish and meat, while carbohydrates such as potatoes, rice and wheat should provide 10 to 20 % of the calorie intake, and fats between 5 to 15 %.

For the first six months, the diet should provide the patient with 800 to 1,000 calories and 75 grams of protein a day.

Foods to avoid

Foods containing sugars should be avoided, firstly because they may hamper weight loss and, secondly, because eating sugary food may lead to a condition called dumping syndrome, which describes when sugar moves directly from the stomach pouch into the small intestine where it can cause palpitations, nausea, abdominal pain and diarrhea.

Liquids should be avoided for a period of 30 minutes before and after eating solid food. When taken together with solids, liquids may cause nausea, as well as pushing food through the stomach pouch at a faster rate, leading to more eating than advised to satisfy appetite.

Overeating should be avoided at all costs. Overeating by even an ounce may induce nausea, vomiting or lead to stretching of the pouch.


Patients must maintain good levels of hydration, with 1 ½ to 2 liters of water consumed every 24 hours. This amount is to be increased by 20% if the patient is sweating. Carbonated beverages, soft fizzy drinks, sweetened drinks, and caffeine-containing drinks need to be avoided.

Maintaining nutrition

Due to the decreased food intake post-surgery, patients are at risk of vitamin and mineral deficiency and diet must be supplemented with multivitamins and minerals for the rest of the patient’s life.

Further Reading

Last Updated: Jun 19, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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