Xenical vs Wegovy: comparing two very different approaches to weight loss

Step 1: understand what each medicine actually does

Xenical is the brand name for orlistat 120mg, a lipase inhibitor that blocks the enzyme your gut uses to digest fat. Roughly a third of the fat you eat passes through unabsorbed rather than entering the bloodstream. The practical consequence is real: if you eat a high-fat meal while taking Xenical, you will likely experience oily stools or urgent bowel movements. The medicine does nothing to appetite signals or hormones, it acts entirely within the digestive tract.

Wegovy belongs to a different class altogether. Semaglutide, its active ingredient, is a GLP-1 receptor agonist. It mimics a gut hormone that tells the brain you have eaten enough, slows how quickly the stomach empties, and reduces overall calorie intake by dampening hunger. You can read the full mechanism on the Wegovy treatment page, and the NHS provides a thorough patient-level overview of semaglutide on its medicines pages.

Orlistat is taken as a capsule three times daily, with meals. Wegovy is a once-weekly subcutaneous injection. Those two facts alone shape which medicine suits a given patient's routine.

Step 2: read the evidence and see where each medicine sits

The clinical trial results tell a clear story about scale of effect. In the STEP 1 trial, published in the New England Journal of Medicine, adults treated with semaglutide 2.4mg over 68 weeks lost an average of around 15% of their body weight alongside lifestyle support. Orlistat trials in similar populations typically showed average losses of 3–5% beyond placebo over twelve months, a meaningful but considerably smaller effect. NICE's appraisal of semaglutide (TA875) reviewed that evidence base and concluded it justified recommendation under specific NHS criteria.

NICE has not issued a technology appraisal for orlistat specifically, so the products sit in different tiers of clinical guidance. That does not make orlistat ineffective (for people who follow the dietary advice carefully, it produces consistent weight loss) but the gap in average outcomes between the two medicines is large and well documented.

The table below summarises the key comparison points.

Step 3: consider which patients each medicine typically suits

Orlistat tends to suit people who would prefer an oral medicine, who eat a diet already moderate in fat, and who want a medicine that has been around for decades with a well-understood safety profile. The catch is dietary discipline: eating fatty meals on orlistat is uncomfortable enough to act as its own deterrent, but that same effect can make social eating stressful.

Wegovy suits adults with BMI 30 or above, or BMI 27 and above alongside a qualifying weight-related condition such as high blood pressure or type 2 diabetes. Its side-effect profile is gastrointestinal too (nausea in particular is common when starting or increasing the dose) but it does not depend on what you eat at a given meal to work. If you want to understand how Wegovy compares with other injectable treatments, the Wegovy comparison overview covers the wider landscape. For a closer look at how semaglutide compares specifically with liraglutide, the Saxenda vs Wegovy page goes into detail on both.

One quick check worth doing before any appointment: look up the pharmacy you're considering on the GPhC pharmacy register. It takes under a minute and confirms whether the pharmacy is legally registered to dispense prescription medicines in the UK. nume's registration number is 9012878.

Step 4: factor in how each medicine is accessed and monitored

Both medicines require a prescription. Neither can be legally supplied in the UK without a clinical assessment confirming suitability. On the NHS, Wegovy access runs through specialist weight management services, and waiting lists are commonly long. Orlistat is more widely prescribed in primary care but still requires a GP or prescriber review.

Privately, a regulated online pharmacy like nume can prescribe Wegovy following a clinical consultation. Our prescribers review your answers, weight and health history the same day, not by algorithm. If you are curious about the full private route for Wegovy, the Wegovy sourcing guide explains what legitimate supply looks like and what to watch out for. Selling prescription medicines without proper clinical oversight is illegal, and the MHRA has warned publicly about fake weight-loss pens circulating online, reporting a suspect seller through Yellow Card helps protect others.

It is also worth knowing that Ozempic, another semaglutide product, is licensed for type 2 diabetes rather than weight loss; the Wegovy vs Ozempic page clarifies the distinction if that question has come up. For a broader look at all the injectable options currently available, how Wegovy sits within the GLP-1 class gives the wider context.

Which of these two medicines is right for you is a clinical decision. Our prescribers work through that with you during your consultation, taking into account your BMI, health history, previous weight-loss attempts and what you want from treatment. Xenical and Wegovy are not interchangeable; they answer different questions. The right answer depends entirely on your picture.