Weight-Loss Jabs or Bariatric Surgery?

Weight-loss injections, widely known as weight-loss jabs, are medicines used to treat obesity and injected under the skin once a week. Their use has grown rapidly in recent years, and many patients who contact us from abroad have already tried them. One of the questions we hear most often is therefore: weight-loss jabs or bariatric surgery? The two treatments are not rivals. Which one is appropriate depends on body mass index, associated conditions and whether the treatment can be sustained over the long term.

What Are Weight-Loss Injections?

Weight-loss injections mimic the effect of GLP-1 (glucagon-like peptide-1), a hormone released by the gut after eating. Newer medicines also mimic a second hormone, GIP.

How They Work:

Fullness: They increase the feeling of fullness by acting on appetite centres in the brain.
Reduced Appetite: Thoughts about food and the urge to eat decrease.
Slower Stomach Emptying: Food stays in the stomach longer, so smaller meals are satisfying.

The medicine is given once a week with a pen injector, and the dose is increased gradually over several weeks to reduce side effects.

Who Are Weight-Loss Injections For?

Adults with a body mass index of 30 or more
Adults with a body mass index of 27 or more who have at least one weight-related condition, such as type 2 diabetes, high blood pressure or sleep apnoea

When They Should Not Be Used:

Pregnancy and breastfeeding
A personal or family history of medullary thyroid cancer or MEN 2 syndrome
Caution is needed in people with a history of pancreatitis.

Important Note: These are prescription medicines that require medical supervision. Products bought online or through social media without a prescription are of unknown content and carry serious health risks.

How Much Weight Can Be Lost With Injections?

Large clinical trials report average weight loss of 15% to 20% after about 16-17 months of treatment combined with a diet and exercise programme. Weight loss is greater with the newer dual-action medicines.

First Months: Because the dose is increased gradually, early weight loss is limited.
Continued Treatment: Weight loss continues over several months and slows after about a year.
Real Life: Missed doses, side effects that prevent dose increases and stopping treatment all change the result considerably.

Do You Regain Weight After Stopping?

Yes. Studies show that about two-thirds of the weight lost is regained within a year of stopping treatment. Improvements in blood sugar, blood pressure and cholesterol largely return towards baseline as well. In patients who continue treatment, the weight loss is maintained.

This confirms that obesity is a chronic disease. To keep the weight off with injections, the medicine usually needs to be taken long term, for most patients indefinitely.

Side Effects

Common Side Effects

Nausea (the most common)
Vomiting, diarrhoea or constipation
Heartburn, indigestion and bloating
Loss of appetite and early fullness

These side effects mostly occur while the dose is being increased, are mild to moderate and ease over time. In some patients, however, they lead to treatment being stopped.

Warning Signs

Severe Abdominal Pain: Severe pain spreading to the back may be a sign of pancreatitis.
Gallbladder Problems: Rapid weight loss can make gallstones more likely.
Dehydration: Persistent vomiting and diarrhoea can affect the kidneys.
Muscle Loss: Low protein intake and inactivity mean part of the weight lost comes from muscle.
Low Blood Sugar: This can occur when used together with diabetes medication.

How Much Weight Is Lost With Bariatric Surgery?

After obesity surgery (gastric sleeve and gastric bypass), most of the weight loss happens in the first 12-18 months. One year after surgery, about 25-30% of total body weight has been lost.

Durability: Ten-year studies show that weight loss is largely maintained after both the sleeve and gastric bypass.
Associated Conditions: Type 2 diabetes, high blood pressure and sleep apnoea improve markedly.
Life Expectancy: In follow-up studies lasting more than 20 years, patients who had bariatric surgery lived about 3 years longer than those who received usual care.

Comparing Injections and Surgery

Weight-Loss Injections

Advantages: No operation or anaesthetic is needed. The dose can be adjusted under medical supervision. In people with obesity and heart disease, they have been shown to reduce the risk of heart attack and stroke.

Disadvantages: Weight returns when they are stopped, so long-term use is needed. Digestive side effects are common. Weight loss is smaller than with surgery.

Bariatric Surgery

Advantages: Greater weight loss. Results have been followed for decades. Marked improvement in type 2 diabetes and other obesity-related conditions. No ongoing weight-loss medication is required.

Disadvantages: Surgical and anaesthetic risks. A gastric sleeve cannot be reversed. Lifelong vitamin supplements and regular follow-up are needed. Long-term problems such as reflux can occur.

For more on the long-term issues of surgery, see Gastric Sleeve Regret: Why It Happens.

Which Treatment for Which Patient?

BMI 27-35: If a weight-related condition is present, medication is usually the first option.
BMI 35-40: With conditions such as type 2 diabetes, high blood pressure or sleep apnoea, surgery is considered.
BMI 40 and Above: Surgery is the main option.
Uncontrolled Type 2 Diabetes: The role of metabolic surgery is assessed separately. See Metabolic Surgery for Type 2 Diabetes for details.
Using Both: The two treatments are not mutually exclusive. Medication can be added for patients who lose too little weight or regain weight after surgery, and some patients with a very high BMI use it to prepare for surgery.

You can check your own value with our BMI calculator, and find an overview of the surgical options on our obesity surgery page.

Travelling for Surgery While Using Weight-Loss Jabs

You can still have surgery, but because these medicines slow stomach emptying, you must tell the surgical and anaesthetic team that you use them before any operation or endoscopy. The team will advise whether to pause the medicine and how to eat before the procedure. If you are travelling for surgery, bring the name and dose of your medicine with you and mention it during your first consultation.

Frequently Asked Questions

Are weight-loss jabs safe?

When prescribed and monitored by a doctor, their side effects are mostly digestive and mild to moderate. Products of unknown origin and use without medical supervision carry serious risks.

How much weight can I lose per month with weight-loss jabs?

Because the dose is increased gradually in the first weeks, early weight loss is limited and varies between individuals. Overall weight loss and whether the treatment can be sustained matter more than a monthly target.

Weight-loss jabs or a gastric sleeve?

For patients with a BMI of 40 or more, or 35 or more with a weight-related condition, a gastric sleeve achieves greater and more lasting weight loss. At a lower BMI, or when surgery is not suitable, medication is usually preferred.

How can I ease the nausea caused by weight-loss jabs?

Eating small portions slowly, avoiding fatty and fried foods and stopping as soon as you feel full reduce nausea. It mostly occurs while the dose is being increased and eases over time. Seek medical advice for persistent vomiting or severe abdominal pain.

Can weight-loss jabs be used in pregnancy?

No. They are not used during pregnancy or breastfeeding. Women planning a pregnancy should discuss with their doctor when to stop the medicine.

Important Warnings

Do not use weight-loss jabs without a prescription and medical supervision.
Do not buy these medicines online or through social media.
Seek medical advice without delay for severe abdominal pain spreading to the back, persistent vomiting or inability to keep fluids down.
Always tell your doctors that you use these medicines before any operation or endoscopy.
Decide on stopping treatment together with your doctor.

Conclusion

Weight-loss jabs are a major advance in obesity treatment and an effective option for the right patient. However, the weight loss they achieve lasts only as long as the medicine is taken; when it is stopped, much of the weight returns. Bariatric surgery provides greater weight loss that is maintained over many years, but it carries surgical risks and requires lifelong follow-up. The right treatment depends on BMI, associated conditions and the patient's goals, and an assessment by a general and bariatric surgeon is recommended before deciding.

References

Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. New England Journal of Medicine, 2021.
Wilding JPH, Batterham RL, Davies M, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, Obesity and Metabolism, 2022.
Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 2022.
Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. New England Journal of Medicine, 2023.
Ghusn W, Vierkant RA, Jawhar N, et al. Metabolic and Bariatric Surgery vs Glucagon-like peptide-1 Receptor Agonist Therapy: A Head-to-Head Comparison in Improvement of Cardiometabolic Risk Profiles. Annals of Surgery, 2026.
Carlsson LMS, Sjöholm K, Jacobson P, et al. Life Expectancy after Bariatric Surgery in the Swedish Obese Subjects Study. New England Journal of Medicine, 2020.
Kindel TL, Wang AY, Wadhwa A, et al. Multisociety clinical practice guidance for the safe use of glucagon-like peptide-1 receptor agonists in the perioperative period. Surgery for Obesity and Related Diseases, 2024.