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Gastric bypass – what should you eat?

Here’s a guide to what to eat after gastric bypass surgery. This is general advice and may need to be adjusted to suit the individual.

Gastric bypass surgery reduces the stomach to the size of a small pouch, which limits how much food you can eat before you are full. The small pouch is directly connected to the middle part of the small intestine. The opening between the stomach and the small intestine is smaller, which makes the stomach empty more slowly, which in turn makes you feel fuller for longer. You get full quickly on just a small amount of food, which enables you to lose a lot of weight.

Appetite is also affected as the contents of the stomach is emptied directly into the middle part of the small intestine. Food bypasses the first part of the small intestine, because it is no longer there, and this means that the body absorbs fewer calories, but also that the absorption of nutrients is impaired, which makes it very important to ensure that the food you eat is nutrient-rich and full of energy.

The less food you eat, the more important what you put on your plate is – so that you meet all your nutritional needs. It is important that the various food groups are included in your daily intake. You also need to take vitamin and mineral supplements for life.

Your food is adjusted several times in the weeks after a gastric bypass:

  • Weeks 0–2: liquid food
  • Weeks 2–6: pureed food
  • Weeks 6–8: finely chopped food, soft food that you chew
  • Week 6 onwards: normal food, eat often and take your time.

Even when eating a normal diet after 6 weeks and beyond, your portion sizes will be much smaller than before the operation. It is important that you take your time, chew your food properly and stop eating when you feel full.

Meal schedule

Eat at 2-3 hour intervals – at least 6 meals a day. The recommended portion size for main meals is 150–200 ml. Chew thoroughly as the passage between the stomach pouch and the small intestine is narrow.

 Main meals: breakfast, lunch and dinner. These meals should preferably take 20 minutes. Eat slowly and chew thoroughly. An example of a lunch might be fish with boiled potatoes and vegetables.

 Snacks: 2–4 per day. Example: cottage cheese with fruit or a boiled egg on wholegrain bread.

Protein should be included in all meals. 

Nutrient-rich food

Because you can’t eat a large amount of food per day, it is very important that your food is rich in protein and nutrients. Eating a moderate amount of all foods can help to ensure that your energy intake is controlled and that you do not eat excessive amounts of any food.

Protein: (provides 4 kcal/gram protein)

  • Dairy products: yoghurt, cottage cheese, quark, fermented milk, milk, skyr, low-fat cheese
  • Poultry
  • Fish/seafood, preferably 2-3 times a week
  • Vegetarian protein: tofu, soy protein, Quorn, legumes
  • Egg
  • Lean red meat

Carbohydrates: (provides 4 kcal/gram carbohydrate)

  • Look for healthier varieties of bread and muesli
  • Root vegetables
  • Potatoes/Sweet potatoes
  • Brown rice
  • Wholegrain pasta
  • Oat groats
  • Quinoa

Fats: (provides 9 kcal/gram fat)

  • Go for liquid fats where possible – use liquid margarine, rapeseed oil or olive oil for cooking and baking.
  • Try low-fat margarine on sandwiches.
  • Avocado
  • Nuts, seeds, nut butters
  • Oily fish
  • Egg yoke

Fats: When you have a gastric bypass, the enzymes and bile reach the food later in the intestine and the fat may not be absorbed in the intestine that remains. This can cause diarrhoea if you eat too much fat.

Avoid/exercise caution with:

  • Stringy foods: asparagus, large quantities of raw food. Eat small pieces and chew thoroughly.
  • Doughy/glutinous foods, for example: white bread, pancakes, white pasta
  • Hard shells: popcorn
  • Empty calories: cakes and biscuits, ice cream, pastries, crisps, sweets, soft drinks. These provide no nutrients – they merely provide energy.
  • High-fat foods that can cause diarrhoea, such as fried foods, rich sauces, crisps…

Liquids

Drink at least 1.5 litres a day – it is a good idea to separate liquids and food so drink between your meals. Drinking too much liquid with a meal can cause poorly chewed food to be washed down and get stuck, but it can also cause dumping (see below). Try measuring out 1.5 litres of liquid in a bottle so you know how much you’re drinking. This drink should be calorie-free, for example water, coffee or tea. Carbonated drinks can cause discomfort as they stretch the stomach pouch.

Alcohol

Alcohol affects you quickly because it goes straight to your intestines and is absorbed much faster. Be careful with alcohol and only drink small amounts. Alcohol is also high in calories and over-consumption can counteract the effects of the operation!

Dumping

This occurs when the body is out of balance, for example when you eat too much food or eat too fast. Symptoms include nausea, vomiting, diarrhoea, palpitations, sweating and fatigue. It can be experienced around eating or a few hours later as a drop in blood sugar. Avoid dumping by following the dietary advice above: eat slowly, chew properly, stop eating when you are full, don’t drink with your meal, eat slow carbohydrates and high-protein foods, and adjust portion sizes.

Constipation

May occur because portions are small and it is difficult to eat enough fibre. Tip: drink enough water, choose carbohydrates that are high in fibre and keep physically active. Regular exercise helps to keep your digestive system working. If this does not help, consult your dietitian.

Vitamin supplements

It is necessary to take life-long vitamin and mineral supplements after gastric bypass surgery due to reduced absorption of nutrients in the intestine and only eating small amounts of food. Monitor your vitamin/mineral levels with regular blood tests. Examples of vitamin supplements: B12 and a complete multivitamin.

Sources 1177.se, Carlanderska.se, Slv.se, Fyss.se

Updated January 18, 2022

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