Bansal, Agam B., et al. "Orlistat." StatPearls - NCBI Bookshelf, 14 Feb. 2024, www.ncbi.nlm.nih.gov/books/NBK542202.
Trying to lose weight can be a disheartening process. You might be doing everything right (eating well, exercising, and living a healthy lifestyle) only to find that the scale is barely budging.
If you're frustrated, you're not alone. More people than ever are turning to weight loss pills, weight loss tablets and weight loss medications to support their goals when diet and exercise alone aren't enough.
You've probably heard about injectable medications like Mounjaro, Wegovy and Saxenda (a class of drugs called GLP-1 receptor agonists). At their highest doses, these can help people lose up to 22.5% of their body weight over 72 weeks.
But if you don't like needles, you might be wondering which weight loss pills actually work, whether tablets are as effective as injections, or how weight loss pills compare to injections overall. Here's what to know about the best weight loss pills available in the UK, plus the Wegovy pill, the first oral GLP-1 now available in the UK.
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Do weight loss pills actually work?
Some do, some don't. The weight loss pills that actually work are those backed by clinical trials and approved by medicines regulators. In the UK, that means prescription weight loss pills like orlistat, the Wegovy pill, and orforglipron (Foundayo).
Most over-the-counter 'slimming pills', 'fat burners' and 'appetite suppressants' sold online haven't been clinically tested. Their effectiveness claims should be treated with caution.
What you should know before taking weight loss pills
Before considering any weight loss medication, there's an important caveat. No pill should be treated as a substitute for diet and exercise. Weight loss drugs work best as part of a comprehensive weight management plan that includes the standard lifestyle advice you're probably following already. Alongside any medication, you should also eat a balanced diet, stay active, minimise stress and get enough sleep where you can.
There are lots of different diet pills on the market, and the landscape can feel a bit like the Wild West. You've probably encountered plenty of dubious products on social media. We'd advise approaching with caution.
Only a few weight loss tablets have been clinically tested and licensed by UK medicines regulators. Four are licensed for weight loss: orlistat, Mysimba (a combination of naltrexone and bupropion), the Wegovy pill, and orforglipron (Foundayo). Of these, orlistat is the only one routinely prescribed on the NHS.
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Weight loss pills to know
Wegovy pill
The Wegovy pill is a once-daily semaglutide tablet and the first oral GLP-1 medicine approved for weight loss. It works the same way as Wegovy injections, reducing appetite, slowing digestion, and helping you feel fuller for longer, but delivered as a daily tablet instead of a weekly jab.
In the OASIS 4 clinical trial, people taking the 25mg dose lost an average of 16.6% of their body weight over 64 weeks, with around one in three losing 20% or more. That makes it the most effective oral weight loss pill currently available in the UK. The Wegovy pill is now approved by the MHRA and available to order with Voy.
Rybelsus
Rybelsus is another oral semaglutide tablet, using the same active ingredient as the Wegovy pill and Wegovy injections but licensed for a different purpose. Where the Wegovy pill is approved for weight loss, Rybelsus is licensed for type 2 diabetes only. In clinical trials, people taking the highest Rybelsus dose lost around 5% of their body weight over 26 weeks, considerably less than the 16.6% seen with the Wegovy pill.
Orlistat
Orlistat is one of two weight loss tablets licensed in the UK (alongside Mysimba). It works by blocking the absorption of fat from food, preventing it from being stored as calories.
Orlistat comes in two strengths. The 60mg version is available over the counter and sold by Voy as Orlos. A higher-strength 120mg version is available on prescription, including through the NHS for some people. You take one capsule up to three times a day, during or within one hour of a fat-containing meal.
It doesn't work for everyone. If, after 12 weeks you haven't lost 5% of your body weight, orlistat probably isn't the right choice for you. But for others, it can be very effective. In a clinical trial, 60% of orlistat patients met that 12-week benchmark. Most of this group (62%) went on to lose more than 10% of their starting weight within a year. In another study, patients taking orlistat lost an average of 5.6% of their body weight within 24 weeks.
Mysimba
Mysimba is a prescription weight loss tablet containing two active ingredients: naltrexone and bupropion. Rather than blocking fat absorption like orlistat, it works on the brain to reduce appetite and food cravings.
In one clinical trial combining Mysimba with intensive lifestyle support, people lost an average of 8.1% of their body weight after 56 weeks. Across other trials, average weight loss was around 3.7-5.7%. Mysimba is licensed for use in adults with a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure.
Mysimba is available in the UK on private prescription, but it isn't routinely prescribed on the NHS. We don't currently offer Mysimba at Voy. It has a more complex side effect profile than orlistat, and we offer orlistat, the Wegovy pill, and GLP-1 injections like Wegovy and Mounjaro.
Glucomannan
Another option is glucomannan, a type of fibre derived from the elephant yam plant. Glucomannan is a dietary supplement rather than a medication, which means it’s not available through the NHS and hasn’t been tested as rigorously as orlistat. But some small studies have found slight benefits for weight loss, at least when combined with a calorie-controlled diet.
Glucomannan Complex
The nutritional supplement for weight loss. One time purchase of a bottle starts from £24.00
Orforglipron (Foundayo)
Orforglipron, sold as Foundayo, is a once-daily GLP-1 weight loss pill, also licensed for type 2 diabetes. It's now approved in both the US and UK, and can be taken at any time of day, with or without food. In clinical trials, people on the highest dose lost up to 12.4% of their body weight over 72 weeks.
Amycretin
A newer oral medication called Amycretin is also in development. It mimics both GLP-1 and amylin hormones, and early trials suggest it could be even more effective than Wegovy. It's still in the clinical trial phase and not yet available on prescription.
How do weight loss pills work?
Oral GLP-1 medicines like the Wegovy pill, Rybelsus and orforglipron (Foundayo) mimic a natural hormone called GLP-1, which reduces appetite, slows digestion, and helps you feel fuller for longer.
Orlistat works by blocking fat absorption in the digestive system. Once you've taken a dose, it travels to the gut, where it stops an enzyme called lipase from breaking down dietary fat. After you've taken this weight loss pill, your body absorbs around 30% less fat than normal, with the rest passed out when you go to the toilet. That equates to around a 200-calorie deficit.
Mysimba combines naltrexone and bupropion, which work on areas of the brain that control appetite and food cravings. The combination helps reduce hunger and the urge to eat.
Glucomannan is a type of soluble dietary fibre, which has been reliably associated with slight weight loss. When we consume soluble fibre, it absorbs water in our body, forming a gel-like consistency. This might help suppress appetite. It might also change the composition of the microbiome (gut bacteria), which can have additional health benefits.
Risks and benefits of weight loss pills
Weight loss pills aren’t a quick fix. And they certainly aren’t a substitute for a healthy diet or exercise. Any claim to the contrary should be taken as too good to be true.
It’s also important to be aware of side effects. Orlistat can have some minor side effects including:
- Abdominal pain
- Diarrhoea
- Flatulence
- Loose, oily stools
These happen because undigested fats are passed out when you go to the toilet. You can minimise these issues by eating a low-fat diet.
If you're interested in taking weight loss medication, speak to a prescriber first. They can help you decide which options might be most appropriate for you.
Side effects support at Voy
"If you're using Voy and you experience any side effects, rest assured that our expert clinicians are just a message or phone call away. They can adjust your dose, prescribe medication to ease your symptoms, or simply offer reassurance.
Everyone responds differently to weight loss treatment and we'll help you find what feels right for you."
Your weight management journey
The internet is full of weight loss pills with bold promises attached. More recently, weight loss patches (sometimes called GLP-1 patches, although they don't actually contain any GLP-1 medicines) have emerged too. The vast majority haven't been well-studied, and some might even be dangerous.
For safe and sustainable weight loss in the UK, the options with the strongest evidence are orlistat, GLP-1 injections like Wegovy and Mounjaro, the Wegovy pill, the first oral GLP-1 approved for weight loss in the UK, and orforglipron (Foundayo).
We can help you find what's right for you. Take a few minutes to fill out our short quiz to see if you're eligible.
DisclaimerAt Voy, we ensure that everything you read in our blog is medically reviewed and approved. However, the information provided is not meant to replace professional medical advice, diagnosis, or treatment. It should not be relied upon for specific medical advice.
Reference
Birketvedt, Grethe Støa, et al. "Experiences with Three Different Fiber Supplements in Weight Reduction." Medical Science Monitor: International Medical Journal of Experimental and Clinical Research, vol. 11, no. 1, 2005, pp. PI5–PI8.
Eli Lilly and Company. "Foundayo™ (Orforglipron)." Foundayo, 2026, foundayo.lilly.com. Accessed 19 May 2026.
