Diet Pills vs GLP-1 Medication

What are diet pills?

The term 'diet pill' is attached to very different products: from harmless fibre supplements to powerful prescription medication. For the consumer this is confusing — and the marketing makes it even less clear.

Scientifically relevant diet pills fall into three categories: (1) supplements without proven clinical effect, (2) proven-effective prescription medication such as Mysimba and orlistat, and (3) GLP-1 receptor agonists (mainly injections, partly pills).

Important principle: anything that promises 'fast weight loss' without diet or exercise is either ineffective or unsafe. Real effectiveness always comes with a mechanism of action that intervenes somewhere in your metabolism or appetite — and that by definition causes side effects.

Categories: over-the-counter vs prescription

Over-the-counter (OTC) weight loss products are bought at the chemist or online without a prescription. Examples: tea extracts, glucomannan, green coffee, garcinia cambogia, CLA, coffee extracts, raspberry ketones, chitosan. Virtually none of these shows clinically significant weight loss in placebo-controlled studies.

Prescription medication requires a consultation with a doctor. Approved in the Netherlands: Mysimba, orlistat (Xenical or generic), Saxenda, Wegovy, Mounjaro, Rybelsus and Ozempic (off-label for obesity). Effective — but only with the right indication and with monitoring.

In-between category: 'illegal' diet pills via Chinese web shops, Telegram channels or unknown online pharmacies. Avoid absolutely. They regularly contain banned substances such as sibutramine or ephedrine and have led to fatal incidents.

Over-the-counter diet pills — what works?

An honest overview of the best-known OTC products and what the science says about them:

• Caffeine: mild thermogenic effect, 50-100 kcal extra burned per day, not clinically relevant for weight loss.
• Green tea/EGCG: studies show a 0.5-2 kg difference compared with placebo, marginal effect.
• Glucomannan (fibre): fills the stomach, gives satiety — 1-2 kg extra over 8 weeks in studies. Safe but modest effect.
• Garcinia cambogia: no consistent effect in meta-analyses.
• Raspberry ketones: no human research confirming an effect.
• Green coffee extract: 1-1.5 kg difference compared with placebo in limited studies of questionable quality.
• CLA (conjugated linoleic acid): small, clinically irrelevant effects.
• Chitosan: marginal fat absorption blockade, virtually no weight loss in studies.
• Yohimbine, l-carnitine, chromium picolinate: no robust evidence.

Clinically effective weight loss medication

What does work requires a prescription and — for the greatest effect — a specialised practitioner. Four main categories are clinically proven.

• Mysimba (naltrexone-bupropion): 5-8% weight loss over 56 weeks. Acts centrally on appetite and reward.
• Orlistat (Xenical/generic): 3-5% weight loss. Works by blocking 30% of fat absorption from food.
• GLP-1 monotherapy (Ozempic, Wegovy, Saxenda): 6-17% weight loss depending on medicine and dose.
• Dual agonists (Mounjaro): 20-22% weight loss — the current gold standard.
• Triple agonists (Retatrutide, from 2026/2027): expected 24%+ in trials.

Mysimba: bupropion-naltrexone

Mysimba is a combination of bupropion (originally an antidepressant and smoking-cessation aid) and naltrexone (originally addiction medication). The combination acts centrally: appetite and the reward system are influenced.

Effect: on average 5-8% weight loss over 12 months in placebo-corrected studies. It works especially for people who 'eat emotionally' or struggle with cravings.

Side effects: nausea (25-30%), headache, insomnia, dry mouth, constipation. In some people raised blood pressure — monitoring before and during treatment is mandatory.

When suitable: BMI ≥30, or BMI ≥27 with comorbidity. Not in uncontrolled hypertension, epilepsy, eating disorders, opioid use or certain psychiatric history.

Costs: ~€100-150 per month, not reimbursed via basic health insurance.

Orlistat (Xenical)

Orlistat blocks the enzyme pancreatic lipase, so that around 30% of the fat from food is not absorbed and ends up in the stool.

Effect: 3-5% weight loss over 12 months. Works best for people with a high-fat diet and consistent use.

Side effects: mainly gastrointestinal — fatty stools, urgency, sometimes incontinence, especially after high-fat meals. Deficiencies of fat-soluble vitamins (A, D, E, K) with long-term use — supplementation is recommended.

When suitable: BMI ≥28 with comorbidity. Can be combined with other medicines. On prescription (Xenical, higher dose) or over the counter (Alli, half dose).

Costs: ~€50-80 per month on prescription.

GLP-1 receptor agonists

GLP-1 medication has been the game changer in weight loss medication since 2021. These medicines work on several levels at once and are 3 to 5 times more effective than classic diet pills.

Mechanism of action: delayed gastric emptying (feeling full for longer), appetite suppression in the hypothalamus, improved insulin sensitivity and direct effects on fat tissue.

Available medicines in the Netherlands: semaglutide (Ozempic 1mg, Wegovy 2.4mg), liraglutide (Saxenda daily), tirzepatide (Mounjaro — dual GLP-1/GIP agonist) and oral semaglutide (Rybelsus).

Effectiveness: Ozempic 6-12%, Wegovy 15-17%, Mounjaro 20-22%, Saxenda 8-10%, Rybelsus 7-9% over 12 months.

Side effects: mainly gastrointestinal — nausea (40-50% during titration, 10-15% long-term), constipation, fatigue. Usually subsiding after 6-8 weeks of titration.

When suitable: BMI ≥30, or BMI ≥27 with comorbidity. At Go Leaner a BIG-registered doctor carries out an individual assessment.

Costs: €299-€600 per month depending on medicine and provider. Wegovy reimbursed when criteria are met.

Oral GLP-1: Rybelsus and orforglipron

For people who would rather not have a weekly injection, there are oral GLP-1 alternatives.

Rybelsus (oral semaglutide) is already available in the Netherlands: a daily tablet, 7-9% weight loss. Drawback: it must be taken on an empty stomach, followed by 30 minutes without eating or drinking. The strict regimen makes it less practical than injections.

Orforglipron (expected 2026/2027): the first non-peptide oral GLP-1, a daily pill without dietary restrictions. Trials show 15% weight loss — comparable to the Wegovy injection. This will probably become the first truly effective oral 'diet pill'.

Important nuance: orforglipron is not yet available on prescription and has not yet been approved by the EMA. The timeline depends on regulatory processes.

Effectiveness comparison in figures

A direct comparison of average weight loss in placebo-corrected 12-month studies:

• Over-the-counter supplements: 0-2 kg (not clinically relevant)
• Orlistat: 3-5%
• Mysimba: 5-8%
• Saxenda (liraglutide): 8-10%
• Ozempic (1 mg): 6-12% (off-label)
• Wegovy (semaglutide 2.4 mg): 15-17%
• Mounjaro (tirzepatide): 20-22%
• Bariatric surgery: 25-35% (reference)
• Retatrutide (expected 2026/2027): 24%+
• When GLP-1 medication is combined with intensive lifestyle intervention: considerably higher than medication alone.

Side effects and risks

No effective weight loss medication is free of side effects. Here are the main profiles:

• Mysimba: nausea, insomnia, headache, raised blood pressure. Not in epilepsy, uncontrolled hypertension, eating disorders.
• Orlistat: fatty stools, urgency, vitamin deficiencies. Not in gallbladder problems, chronic malabsorption.
• GLP-1: nausea, constipation, fatigue, rarely pancreatitis. Not in medullary thyroid carcinoma (MEN-2 syndrome), pregnancy, severe gastroparesis.
• Avoid absolutely: ephedrine, sibutramine, DNP, illegally sold 'miracle' pills — can be seriously cardiotoxic or hepatotoxic.

Dangerous diet pills to avoid

A warning about products that turn up in the Netherlands or online and have caused serious health damage.

• Sibutramine: off the market since 2010 because of cardiovascular mortality. Still sold illegally in 'herbal pills' from Asia.
• DNP (2,4-dinitrophenol): a very effective fat burner but lethal from 5-7 mg per kg of body weight. Dozens of deaths worldwide each year.
• Ephedrine and ephedra: cardiovascular risk, only permitted on prescription in the Netherlands.
• T3 (thyroid hormone): used by bodybuilders without thyroid deficiency, causes heart problems and muscle breakdown.
• Diuretics for 'water loss': the weight loss is purely fluid, causes dehydration damage.
• Laxatives for weight loss: no lasting weight loss, damage to the intestines.
• General red flags: offered without prescription, claims of >5 kg per week, available via Telegram or Chinese web shops, ingredients in a foreign language, no GP or pharmacy stamp.

Which one suits you?

The choice depends on BMI, comorbidity, lifestyle and personal preferences. A rough guide:

• BMI 25-27 without comorbidity: lifestyle approach first. No indication for medication.
• BMI 27-30 with comorbidity (diabetes, hypertension, dyslipidaemia): Mysimba, Saxenda or off-label GLP-1.
• BMI 30-35: GLP-1 (Ozempic, Wegovy or Mounjaro) is most effective. Orlistat as a budget alternative.
• BMI ≥35: Wegovy or Mounjaro — possibly reimbursed via basic health insurance. If these fail, alternative: bariatric surgery.
• BMI ≥40 (morbid obesity): Wegovy/Mounjaro or bariatric surgery — both reimbursed provided the conditions are met.
• Preference for a pill rather than an injection: Mysimba, Orlistat, Rybelsus (oral GLP-1) or, in 2026/2027, orforglipron.