Orlistat is one of the few weight loss medicines that works inside the gut rather than on appetite. It is taken with meals and stops part of the fat you eat from being absorbed. That makes it quite different from other treatments, and it means the first three months depend heavily on what is on your plate. Here is a realistic picture of what to expect.
How orlistat works
Orlistat blocks lipase, the enzyme your gut uses to break down fat. When lipase is blocked, roughly a quarter to a third of the fat in a meal passes through without being absorbed. Those calories never reach your body. Orlistat does not suppress hunger, speed up metabolism or burn fat you already carry. It simply reduces the fat you take in, so it works best alongside a reduced-calorie, lower-fat diet.
The usual dose
The prescription dose is 120 mg, taken three times a day with each main meal that contains fat, or up to an hour after the meal. If you skip a meal, or eat a meal with no fat, you skip that dose. A lower 60 mg strength is also used in some places. Taking more than prescribed does not increase weight loss.
Weeks 1 to 4: learning the rules
The first month is when most people discover how much fat their usual meals contain. Fat that is not absorbed has to leave the body, so a fatty meal can lead to oily stools, wind with an oily discharge, urgency or loose stools. These effects are a direct signal that the meal had too much fat. Most people find they settle once meals are kept to around 30% of calories from fat, spread evenly over three meals.
- Spread fat across the day rather than saving it for one big meal.
- Check labels for fat per serving and choose lower-fat versions.
- Keep a spare change of underwear handy for the first few weeks, just in case.
Weeks 4 to 12: the first results
With a calorie-controlled diet, steady weight loss usually becomes visible over the first three months. A common review point is 12 weeks: if you have not lost at least 5% of your starting weight by then, your prescriber may suggest stopping, because orlistat is unlikely to help much more for you. If you have, continuing alongside diet and activity usually adds further loss over the following months.
Vitamins and other medicines
Because orlistat reduces fat absorption, it can also reduce absorption of fat-soluble vitamins (A, D, E and K). Many prescribers suggest a multivitamin taken at bedtime, at least two hours away from an orlistat dose. Orlistat can also affect some other medicines, including ciclosporin, levothyroxine, some epilepsy medicines and warfarin, and it may make the contraceptive pill less reliable if it causes severe diarrhoea. Tell your prescriber and pharmacist about everything you take.
Who should not take it
Orlistat is not suitable during pregnancy or breastfeeding, or for people with long-term problems absorbing food from the gut or with cholestasis (reduced bile flow). Your prescriber will check this before you start.
Ordering and cost
Three doses a day add up over several months, so many people choose a generic. Generic orlistat 120 mg contains the same active ingredient as the original brand. If you buy generic orlistat online, a valid prescription is required, and the strength on the pack should match your prescription. Whenever you buy medicine online, keep the patient leaflet and read it before the first dose. This guide to orlistat for weight loss covers results and side effects in more depth, and the weight loss range lists the current generic packs.
Want to go further? You can see Orlijohn 120 (orlistat 120 mg), or browse everything on the RxPillTab store.
This is general information, not medical advice. Speak to your doctor or pharmacist before starting any medicine.