Bariatric surgery and the common effects on your diet

This guide has been written by Dr Mabel Blades, PhD. M.IFST.  B.Sc.(Hons), RD, D.M.S., M.Phil., M.B.D.A., R.S.H., Independent Dietician and Nutritionist

You can download a printable version of this guide here.

There are various types of procedures to assist with weight loss, including gastric bands, gastric balloons, endo-barriers placed in the small intestine, gastric bypass procedures, as well as “virtual procedures” based on hypnosis. Here we will focus primarily on gastric bands and gastric bypass procedures.

Normally prior to any gastric band or gastric bypass surgery there is a full discussion of the procedure, as well as the consequences of it; for example what can be eaten and drunk after the surgery.

Prior to any procedure advice is usually provided by a dietitian about a pre-operative diet to make the surgery easier and to improve recovery, enabling people to ensure they can cope with the future restrictions on intake.

Common effects after the surgery:

After surgery the following is common:

  • There is a period of weaning after the procedure which usually takes about 6-8 weeks, starting with fluids only and gradually moving through purees to softer foods and finally foods with more texture
  • Pain, vomiting, poor healing and dislocation of the gastric band can occur if the progressive diet after the procedure is not followed
  • The stomach capacity is markedly reduced. Initially after the procedure the stomach capacity is the size of a walnut, eventually expanding to that of an individual small pot of yoghurt.
  • Large meals cannot be eaten again. Only small portions of foods can be eaten or vomiting can occur.
  • Food and fluids should not be taken together. This can lead to vomiting or stretching the stomach. A 30 minute gap is needed.
  • Protein foods should be the basis of future diets.
  • Foods should be eaten slowly. Food must be chewed 15-20 times so it forms a paste and thus a meal can take a considerable time to eat which can make eating out difficult.
  • Pasta, rice, bread, raw vegetables and roasted and grilled meat and similar drier foods can cause discomfort.
  • Fluids require to be sipped slowly throughout the day. 1.5 litres of fluid is required
  • Constipation can occur if not enough fluid is taken
  • Fizzy drinks should be avoided
  • Vitamin and mineral supplements are required for life
  • Injections of vitamin B12 are required every three months after gastric bypass surgery
  • Sweet foods must be avoided. Chocolate, sweet biscuits, cakes and puddings can all cause dumping syndrome with diarrhoea, sweating and nausea.
  • Constant snacking will not be possible
  • Alcohol has a much greater effect and blood alcohol levels are increased
  • Foods can “stick” between the stomach and intestine. This causes discomfort.

It is also worth being aware of the effects that rapid weight loss can have, including: aches and pains, tiredness and feeling cold, dry skin, mood changes, hair loss or thinning hair, folds of skin plus relationship difficulties.

Get in touch






We will only use data from this form to process your enquiry.