Orlistat vs Wegovy in Australia

No randomised trial has compared orlistat with semaglutide at any dose. A Europe PMC search for randomised controlled trials of orlistat with semaglutide or tirzepatide, run 6 October 2026, returned placebo-controlled trials and post-hoc analyses only.

Orlistat blocks the gut enzymes that break down dietary fat, so about 30% of the fat eaten passes through unabsorbed. Wegovy acts on appetite and slows stomach emptying. The figures below are from the Australian Product Information for each, not the American labels, which differ.

Orlistat: the signature effects are the fat passing through. The Product Information lists oily spotting, wind with discharge, urgent bowel movements, fatty or oily stools, liquid stools, more frequent bowel movements and faecal incontinence as "commonly or very commonly observed". They occur within the first three months, most people have only one episode, and they get worse the more fat a meal contains. The Australian document gives categories, not percentages; the American label, reporting the same seven trials, puts oily spotting at 26.6% against 1.3% on placebo in year one, faecal urgency at 22.1% against 6.7% and faecal incontinence at 7.7% against 0.9%. Soft stools, nausea, indigestion, headache and tiredness are common (1 to 10%). Rare post-marketing reports include severe allergic reactions, pancreatitis, hepatitis and severe liver injury (no causal relationship established, the document says) and oxalate kidney damage. Vitamin D, vitamin E and beta-carotene levels fell more than on placebo; the document recommends a multivitamin.

Wegovy: nausea, diarrhoea, constipation and vomiting are the common effects and they cluster around each dose increase. In the pooled trials 38.3% had nausea against 14.0% on placebo, 26.8% diarrhoea against 14.3%, 21.8% constipation against 10.2% and 21.8% vomiting against 5.7%. Gut effects led 4.3% to stop permanently. Adjudicated pancreatitis was 0.2% against less than 0.1%. The Consumer Medicine Information lists symptoms needing urgent attention: severe and long-lasting pain in the stomach, which may spread to the back (possible pancreatitis); breathing problems, swelling of the face or throat, or wheezing (allergic reaction); loss of vision; and severe constipation with stomach ache, bloating or vomiting (bowel blockage).

Orlistat 120 mg for weight control is Schedule 3, a Pharmacist Only Medicine, under the Poisons Standard of June 2026. No prescription is required by law; a pharmacist must supply it and check it is appropriate. Online, Chemist Warehouse and Chemist Outlet will not dispatch until you have spoken to their pharmacist by phone; Your Discount Chemist labels it "Prescription Only Medicine" and will not dispatch without a script, which is that retailer's policy rather than the law. The Product Information criteria are a BMI of 30 or more, or 27 or more with other risk factors, with a mildly reduced-energy diet in which no more than 30% of calories (about 67 g a day) come from fat. It is not recommended under 18; Wegovy is registered from age 12.

Wegovy is Schedule 4, prescription-only. A GP, a specialist or a nurse practitioner (within their scope of practice; rules vary by state and territory) can write a private script for an adult with a BMI of 30 or more, or 27 to 30 with at least one weight-related condition such as prediabetes, high cholesterol, high blood pressure, osteoarthritis or sleep apnoea, alongside a reduced-energy diet and more physical activity. The telehealth services that advertise weight-loss programs (Juniper, Hims, Moshy, Mosh, Youly, hub.health, InstantScripts and others) sell a monthly bundle of consultations, medicine and delivery; which medicine and dose you get is decided at the consultation.

Compounded semaglutide has been illegal to make or supply in Australia since 1 October 2024, and in March 2026 the TGA reported that imported unregistered products labelled as GLP-1 contained none.

For weight loss, Wegovy, on every measure available: 12.4 percentage points more than placebo over 68 weeks in STEP 1, and 9.8% against lifestyle alone at one year in the 2026 network meta-analysis, where orlistat's effect was not convincingly different from lifestyle change alone; the older orlistat reviews give 2.6 to 2.9 kg more than placebo. The two have never been tested against each other, so the size of the gap is an estimate, but no analysis puts orlistat close.

Orlistat is cheaper (about $95 against $370 for 28 days at Chemist Warehouse on 9 November 2026), needs no prescription, no injection and no dose escalation, and its side effects stay in the gut. The RACGP's journal, in April 2025, places incretin medicines such as Wegovy first for people with type 2 diabetes, cardiovascular disease, sleep apnoea or fatty liver disease, and orlistat as an option for people with cardiovascular disease or hypertension where incretin medicines are not tolerated or not affordable.

No Australian guideline covers moving from orlistat to Wegovy or back, neither Product Information mentions the other medicine, and neither supports taking the two together: the orlistat document says use with any other anti-obesity agent is not recommended because no interaction studies exist, and the Wegovy document says it has not been studied with other weight-management products.

A switch is a stop and a start. Orlistat has no dose escalation and no washout period in its Product Information. Wegovy starts at 0.25 mg for everyone and steps up every four weeks to 2.4 mg by week 17, with the gut side effects concentrated in that period. No study of the sequence in either direction was found.

Weight regain after stopping either medicine is documented. A year after stopping semaglutide in the STEP 1 extension (an exploratory subset of 327 participants), people had regained two thirds of what they lost; Australian Prescriber's December 2025 review says regaining weight after stopping is the norm. For orlistat, the Product Information warns of "possible weight regain and/or attenuation of weight loss" after one year, and the 2007 pooled review found that in trials with a second year the orlistat and placebo groups regained weight at a similar rate, with the gap between them preserved.