- Serious complications nationally: 1.4% (DATO 2024).
- Lifelong WLS vitamins and calcium, not reimbursed.
- Bypass: dumping and internal hernia; sleeve: reflux.
- Temporary hair loss and loose skin are common.
- Some weight can return after five to ten years.
What are the main disadvantages of weight loss surgery?
The most structural disadvantage is that you absorb fewer nutrients, especially after a bypass. Without supplements, deficiencies of iron, vitamin B12 and folic acid develop, and to a lesser extent zinc, selenium and vitamins A, E and K. You therefore take a WLS multivitamin and calcium with vitamin D for life, and have your blood checked regularly.
Other disadvantages depend on the operation. After a bypass, dumping can occur after sugar or fat, and an internal hernia occurs in about 1 to 1.5 percent. After a sleeve, reflux can increase, and the operation cannot be reversed. After every procedure, anti-inflammatory painkillers (NSAIDs) are forbidden.
Complications around the operation
The most serious early complication is leakage at a staple line; it is rare but can require a new operation. Pain and nausea are common in the first days. Bleeding and thrombosis are prevented with careful technique, early mobilisation and a daily thrombosis injection. In the DATO register, 1.4 percent of Dutch patients had a serious complication in 2024.
What are the long-term disadvantages?
Weight loss holds well for up to about ten years, but some weight can gradually return after five to ten years, often because eating habits change. Deficiencies can appear years later if vitamins are forgotten. After a bypass the risk of kidney stones is higher, and after fast weight loss gallstones are more common; the Nederlandse Obesitas Kliniek mentions a risk of about twenty percent.
Alcohol reaches the blood faster and at higher levels after a bypass, and a minority develops alcohol problems. Research into mental effects and quality of life in the long term is still limited.
Disadvantages weighed against the benefits
Advantages
| Advantage | Explanation |
|---|---|
| Lasting weight loss | about 20-40% of total body weight |
| Type 2 diabetes | often less or no medication after a bypass |
| Other conditions | sleep apnoea, blood pressure and joint pain often improve |
| Monitored care | every operation recorded in DATO |
Points of attention
| Point of attention | Explanation |
|---|---|
| Complications | 1.4% serious nationally (2024) |
| Deficiencies | lifelong supplements and blood tests |
| Dumping / reflux | depending on the operation |
| Alcohol | stronger effect after a bypass |
Cost and insurance (2026)
Some disadvantages are financial: several costs remain your own for life.
| Item | Amount or arrangement |
|---|---|
| Operation (with indication) | €385 deductible 2026 |
| Vitamins and calcium | €10-€15 a month, not covered |
| Skin surgery | not always covered |
| Revision with medical reason | basic package |
Risks and disadvantages: key figures
| Feature | Value |
|---|---|
| Serious complications (2024) | 1.4% |
| Internal hernia after bypass | about 1-1.5% |
| Gallstones after fast weight loss (NOK) | about 20% |
| Hair loss starts | 3-6 months after surgery |
| Weight loss holds well | up to about 10 years |
Disadvantages per operation
| Disadvantage | Gastric sleeve | Gastric bypass |
|---|---|---|
| Dumping | rare | common |
| Internal hernia | not applicable | about 1-1.5% |
| Reflux | can increase | usually decreases |
| Reversible | no | technically possible |
| Deficiencies | moderate | more likely |
Step by step
- Know the risks. Read per operation what applies to you.
- Screening. Discuss your own risk profile.
- Prevent. Stop smoking, take vitamins, avoid NSAIDs.
- Recognise. Know the warning signs after surgery.
- Follow up. Blood tests for at least five years.
Read next
- Gastric bypass disadvantages — including alcohol
- Sleeve or bypass — which risks fit you
- Aftercare that limits the risks — check-ups
- Types of weight loss surgery — all operations
How to reduce the risks yourself
Stop smoking well before surgery, keep your weight stable during the preparation and follow the food build-up after the operation. Take your WLS vitamins and calcium every day, never use NSAIDs and keep attending check-ups, including in the later years.
Learn the warning signs: increasing abdominal pain, fever, a fast heartbeat, persistent vomiting, black stools or sudden cramping pain after eating. Contact your centre straight away when they occur; early treatment makes a big difference.
Write the phone number of your centre's medical helpline in your phone before the operation, so you do not have to search for it when you need it.
Frequently asked questions about the risks and disadvantages
For most people it is the lifelong need for vitamins and calcium, because fewer nutrients are absorbed. Without supplements, deficiencies can develop, even years after surgery.
The risk profile is favourable. Nationally, 1.4 percent of Dutch patients had a serious complication in 2024. The most serious early complication, a leak at a staple line, is rare.
Yes. Weight loss holds well for up to about ten years, but some weight can gradually return after five to ten years, often because eating habits change.
Not everyone, but it is common after major weight loss, depending on age and how much weight is lost. Only surgery removes it, and that is not always reimbursed.
Sweating, palpitations, dizziness or sleepiness when sugar or fat reaches the small intestine too fast, mainly after a bypass. It usually passes within about 45 minutes.
Painkillers such as ibuprofen, naproxen and diclofenac can cause an ulcer, especially at the connection after a bypass. Paracetamol is usually allowed.
After a bypass alcohol reaches the blood faster and at higher levels and stays longer. Doctors at Ghent University Hospital increasingly advise against alcohol after this operation.
Fast weight loss increases the risk of gallstones; the Nederlandse Obesitas Kliniek mentions about twenty percent. Report pain in the upper abdomen to your centre or GP.
No. Hair loss usually starts three to six months after surgery, is temporary and recovers by itself. Keep taking your vitamins daily.
For most people who meet the criteria, yes: lasting weight loss and often improvement of diabetes, sleep apnoea and other conditions. It does require lifelong discipline with vitamins, food and check-ups.
Call +31 6 38048347 (Mon–Fri 09:00–17:00) or email info@maagverkleining-info.nl. This page is also available in Dutch.
Sources
- DATO Annual Report 2024, DICA
- Vitalys (Rijnstate): FAQ
- WeightWorks: gastric bypass and mini gastric bypass
- Nederlandse Obesitas Kliniek: gallstones
- Druglijn and VRT NWS (Ghent University Hospital): alcohol after bariatric surgery
Search terms leading here: weight loss surgery risks, bariatric surgery disadvantages, side effects of gastric bypass, long term effects weight loss surgery.
Author: Gijs Bodenstaff. Last reviewed: September 2026.