In this article
- • What GLP-1 is as a hormone
- • How GLP-1 works in the body
- • What a GLP-1 receptor agonist is
- • Which GLP-1 medicines are available
- • How much weight you can lose with GLP-1
- • Who GLP-1 is suitable for
- • Side effects and risks
- • What GLP-1 costs in the Netherlands
What GLP-1 is as a hormone
GLP-1 stands for glucagon-like peptide-1, a hormone that is naturally produced in the small intestine. When you eat, cells in the gut wall release GLP-1 into the blood. There it acts on several organs at once: the brain, the stomach and the pancreas. Together these effects ensure that you feel full, your blood sugar stays stable and you do not get hungry again too quickly.
The problem is that natural GLP-1 only circulates in the blood for a few minutes before it is broken down by the enzyme DPP-4. In people with obesity or type 2 diabetes, this response also appears to be blunted. That is where GLP-1 medication steps in.
GLP-1 medication is a synthetic version of the hormone that is specifically designed not to be broken down. As a result, the effect lasts for days to a week instead of minutes. That provides the continuous satiety effect and the blood sugar regulation that make it so effective for weight loss.
How GLP-1 works in the body
GLP-1 works through three main mechanisms that reinforce one another. The central effect is appetite suppression in the hypothalamus: GLP-1 activates receptors in the satiety centre, so you feel full sooner and experience less hunger between meals.
The second effect is slowed gastric emptying. Food stays in the stomach longer, so blood sugar peaks less sharply and the feeling of fullness lasts longer. This is also the reason GLP-1 medication can cause nausea as a side effect, especially in the titration phase.
The third effect is in the pancreas: GLP-1 stimulates insulin release only when blood sugar is too high, while simultaneously suppressing glucagon release. That makes GLP-1 monotherapy safe with regard to hypoglycaemia: unlike insulin, it rarely causes blood sugar to drop too low.
What a GLP-1 receptor agonist is
A GLP-1 receptor agonist is a medicine that activates the same receptors as the natural GLP-1 hormone. 'Agonist' literally means: a substance that triggers a biological effect by activating a receptor. In this case the molecule imitates GLP-1 but remains active for much longer.
There are now two subclasses on the market. Single agonists activate only the GLP-1 receptor (semaglutide in Ozempic, Wegovy, Rybelsus; liraglutide in Saxenda). Dual agonists activate both the GLP-1 and the GIP receptor (tirzepatide in Mounjaro and Zepbound), which makes them more effective for weight loss. A third generation, triple agonists such as retatrutide, also activates the glucagon receptor.
For a more in-depth explanation of the active substances, see our pages on semaglutide and tirzepatide.
Which GLP-1 medicines are available
In the Netherlands, four GLP-1 medicines are currently EMA-approved and available through pharmacies: Saxenda (liraglutide, daily injection), Ozempic (semaglutide, weekly injection for diabetes), Wegovy (semaglutide, weekly injection for obesity) and Mounjaro (tirzepatide, weekly injection for diabetes and obesity).
In addition, Rybelsus is the oral tablet form of semaglutide, also from Novo Nordisk. Mysimba is not a GLP-1 but is sometimes mentioned in the same context: it is a combination of naltrexone and bupropion and works through a different pathway on the brain's reward centre.
Expected in 2026-2028: retatrutide (Eli Lilly's triple agonist, phase 3) and orforglipron (Eli Lilly's oral tablet, phase 3). Zepbound is the American version of Mounjaro and is not available in the Netherlands.
How much weight you can lose with GLP-1
Weight loss in clinical studies varies considerably between medicines. Saxenda (liraglutide 3 mg) gives an average of 5-7% weight loss over 56 weeks. Ozempic (semaglutide 1 mg) around 10-12% over 68 weeks. Wegovy (semaglutide 2.4 mg) reaches 15-17%. Mounjaro (tirzepatide 15 mg) is currently the most effective EMA-approved option, with 18-22% weight loss over 72 weeks.
Important: these figures are averages from controlled trials in which participants also received intensive lifestyle coaching. Real-world results in a Dutch clinic setting are usually 2-4% lower than trial figures, mainly because patients follow the diet and exercise advice less strictly.
The effect builds up over the first 6-12 months and then stabilises. As long as the medication is continued and the lifestyle changes are maintained, weight usually remains stable. If the medication is stopped without lasting lifestyle changes, most of the weight returns within 6-12 months.
Who GLP-1 is suitable for
The international guidelines for GLP-1 in weight loss use as their primary criterion: a BMI of 30 kg/m² or higher. With a BMI between 27 and 30 (overweight without obesity), GLP-1 is also indicated provided there are one or more weight-related conditions such as type 2 diabetes, hypertension, dyslipidaemia or sleep apnoea.
For patients with type 2 diabetes, GLP-1 is now the second-line choice after metformin when glucose control is insufficient. For that indication, Mounjaro and Ozempic are reimbursed under basic health insurance. For the obesity indication without diabetes, stricter GVS reimbursement rules apply (GVS is the Dutch medicines reimbursement system), and only a proportion of patients qualify.
GLP-1 is not suitable for people with a personal or family history of medullary thyroid carcinoma, MEN2 syndrome, active pancreatitis, pregnancy, breastfeeding or severe hypersensitivity to the active substance.
Side effects and risks
The most common side effects are gastrointestinal: nausea (20-44%), diarrhoea (10-30%), constipation (10-25%) and vomiting (10-24%). These occur mainly in the titration phase and usually disappear after 4-12 weeks once the dose is stable. The titration schedule (gradual dose increase) is specifically designed to limit this.
Rare but serious side effects: acute pancreatitis, gallbladder inflammation, gallstones due to rapid weight loss, worsening of diabetic retinopathy. For Wegovy and Mounjaro, the SELECT and SURMOUNT trials demonstrated a reduction in cardiovascular events, which makes the net risk profile positive.
One specific point of attention is 'Ozempic face' — loss of facial volume due to rapid weight loss. This is not a GLP-1-specific effect but a consequence of substantial weight loss in a short time. The effect is largely reversible with a collagen-rich diet and, if desired, cosmetic interventions.
What GLP-1 costs in the Netherlands
Monthly costs range from €100 to €250 depending on the medicine and the dose. Saxenda costs around €120-180 per month, Ozempic €106-190, Wegovy €140-190, Mounjaro €200-400 (highest at the maximum dose), Rybelsus €110-170.
For type 2 diabetes, Ozempic and Mounjaro are reimbursed under basic health insurance after metformin. For the obesity indication without diabetes, GVS criteria apply: Wegovy and Saxenda can be reimbursed with a BMI of 35 or above plus additional comorbidity and a documented lifestyle intervention.
At Go Leaner we work with transparent all-in monthly prices: medication + monthly doctor check-up + lifestyle coaching + blood tests included. You will find the exact rates per medicine and programme on our pricing page.
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GLP-1 is always prescribed by a BIG-registered doctor after a medical assessment. This article is for information purposes and does not replace a medical consultation.