- Sugar and fat: can cause dumping after a bypass.
- No drinking half an hour before and after meals.
- Careful with alcohol, especially after a bypass.
- No NSAIDs: ibuprofen, naproxen, diclofenac, meloxicam.
- No fasting in the first year.
Which foods and drinks should you avoid?
Sugary foods and drinks such as soft drinks, juice, sweets and pastries can cause dumping after a bypass and add many calories after any operation. Fatty and fried food can do the same. Sweet dairy contains milk sugar, a fast sugar; sour dairy such as buttermilk, quark and yoghurt is better tolerated.
Food that is chewed too coarsely can get stuck and cause pain and vomiting, which in turn causes swelling and makes passage harder. Take small bites and chew very well.
Medicines and supplements to avoid
Anti-inflammatory painkillers (NSAIDs) are forbidden after weight loss surgery: ibuprofen, naproxen, diclofenac and meloxicam, also under brand names such as Advil, Aleve and Voltaren. They can cause an ulcer. Paracetamol is usually safe. A regular multivitamin contains too little; use a WLS multivitamin for your operation. During pregnancy, do not switch to regular pregnancy vitamins on your own.
Habits to avoid
Drinking with meals flushes food through the small stomach; keep at least half an hour between eating and drinking. Grazing, eating small amounts all day, and liquid calories undermine weight loss in the long term.
Fasting is discouraged in the first year, because you lose weight fast and your reserves are low. After that, discuss it with your team.
Better choices
Advantages
| Advantage | Explanation |
|---|---|
| Water and tea without sugar | between meals |
| Sour dairy | buttermilk, quark, yoghurt |
| Protein first | egg, fish, chicken, legumes |
| Paracetamol | usually allowed for pain |
Points of attention
| Point of attention | Explanation |
|---|---|
| Soft drinks and juice | sugar and dumping |
| Fried food | fat and dumping |
| NSAIDs | risk of ulcers |
| Regular multivitamin | too little after surgery |
Cost and insurance (2026)
Avoiding the wrong products does not cost extra; the right supplements do.
| Item | Amount or arrangement |
|---|---|
| WLS vitamins and calcium | €10-€15 a month |
| Paracetamol | pharmacy or drugstore |
| Dietitian in aftercare | covered |
What not to eat: key figures
| Feature | Value |
|---|---|
| Between eating and drinking | at least 30 minutes |
| Meals per day | 6 |
| Dairy portions | 2-3 sour ones a day |
| Fasting | not in the first year |
| Forbidden painkillers | all NSAIDs |
Avoid and choose instead
| Avoid | Why | Choose instead |
|---|---|---|
| Soft drinks, juice | sugar, dumping | water, tea without sugar |
| Sweet yoghurt drinks | milk sugar | buttermilk, plain yoghurt |
| Ibuprofen, naproxen | ulcer risk | paracetamol (usually) |
| Regular multivitamin | too little | WLS multivitamin |
Step by step
- Check your cupboard. Remove NSAIDs and sugary drinks.
- Shop. Protein, vegetables, sour dairy.
- Plan. Six small meals a day.
- Pharmacy. Tell them about your operation.
- Review. Discuss problem foods with your dietitian.
Read next
- Diet after surgery — phases
- Dumping syndrome — triggers
- Alcohol after surgery — risks
- Vitamins after surgery — which ones
Tell every pharmacist and doctor
Pharmacists in the Netherlands register your medication and can warn about interactions, but only if they know about your operation. Mention it at every new prescription and when buying painkillers over the counter, and ask your GP to record it in your file.
Some medicines are absorbed differently after a bypass, such as the contraceptive pill. When in doubt, ask whether a different form or dose is needed.
Eating out and travelling
Restaurants and hotel buffets make it easy to overeat or drink with meals. Choose small portions, skip sugary desserts and drinks, and take your vitamins with you when travelling.
A simple rule of thumb
If a food or drink is sweet, fatty, fizzy or liquid with many calories, think twice. If it is rich in protein, eaten slowly and chewed well, it usually fits. When in doubt, try a small amount at home first, not at a dinner or party.
Keep a short list of products that cause you problems and share it with your dietitian. Everyone reacts differently, and your list will be personal.
Medicines: questions to ask
Is this medicine safe after my operation? Does the form matter, for example a tablet versus a liquid? Is it absorbed differently after a bypass? Asking these questions at the pharmacy prevents problems.
When you slip up
Everyone eats something that does not agree with them now and then. If it causes dumping, lie down and let it pass; if food gets stuck, stop eating and wait. Learn from it rather than feeling guilty, and mention repeated problems to your dietitian.
Reading food labels
Check labels for added sugars and fat, and be aware that 'light' or 'low fat' products can still contain a lot of sugar. Portion size matters too: a small portion of a suitable product is better than a large one.
Your dietitian can help you read labels.
Frequently asked questions about what to avoid
Mainly sugar and fat, such as soft drinks, juice, sweets, pastries, sweet dairy and fried food, because they can cause dumping.
No. Keep at least half an hour between eating and drinking so food is not flushed through.
All NSAIDs: ibuprofen, naproxen, diclofenac and meloxicam, also as Advil, Aleve or Voltaren. Paracetamol is usually allowed.
No, it contains too little. Use a WLS multivitamin for your type of operation.
Be very careful, especially after a bypass: alcohol peaks faster and higher. Many specialists advise against it.
Not in the first year. Afterwards, discuss it with your team.
Milk sugar is a fast sugar that can trigger dumping; sour dairy is better tolerated.
Stop eating, and next time take smaller bites and chew better. Persistent vomiting needs contact with your centre.
Many centres advise against them, especially sugary ones; ask your dietitian about sugar-free options.
Not instead of your WLS multivitamin. Add folic acid as advised, but do not switch on your own.
Call +31 6 38048347 (Mon–Fri 09:00–17:00) or email info@maagverkleining-info.nl. This page is also available in Dutch.
Sources
- Vitalys (Rijnstate): FAQ, medication and supplements
- Ziekenhuis Rivierenland: diet after surgery
- St. Antonius and Amsterdam UMC: dairy after weight loss surgery
- Druglijn and VRT NWS: alcohol after a bypass
Search terms leading here: what not to eat after gastric bypass, foods to avoid after weight loss surgery, medicines to avoid after bariatric surgery.
Author: Gijs Bodenstaff. Last reviewed: September 2026.