Orlistat

About Orlistat

Orlistat 120mg is a prescription-only capsule taken with meals to support weight loss. It contains the same active ingredient as Xenical, in generic form, and works in an entirely different way from the GLP-1 medicines, locally in the digestive tract rather than on appetite.

Expected weight loss

Orlistat produces more modest results than GLP-1 treatments. Clinical evidence supports around 5% of body weight over a year when combined with a reduced-calorie, low-fat diet, roughly 3kg more than diet alone. For someone weighing 100kg, that is around 5kg.

NICE guidance suggests reviewing treatment at 12 weeks and continuing only if you have lost at least 5% of your starting weight.

Who is it for?

Orlistat is a sensible choice if you want prescription support at a lower cost, if GLP-1 medicines are unsuitable for you, or if you would rather avoid a medicine that acts on appetite signalling. It works best for people whose eating pattern is genuinely fat-heavy, since that is what it acts on.

Realistic expectations

Orlistat is not a licence to eat freely. It works alongside a low-fat diet, and if you do not follow one, the side effects will make that very clear very quickly.

How Orlistat works

Dietary fat arrives in your gut as triglycerides, molecules far too large to cross the intestinal wall. An enzyme called lipase, produced by the pancreas, breaks them into smaller fatty acids and monoglycerides that can be absorbed.

Blocking the enzyme

Orlistat binds to gastric and pancreatic lipase and inactivates it. With less lipase available, roughly 30% of the fat in your meal is never broken down, so it passes through the digestive system and is excreted.

The calorie arithmetic

Fat carries 9 calories per gram. A meal with 30g of fat contains 270 calories from fat alone; orlistat prevents around 80 of those from being absorbed. Across three meals a day this adds up to a meaningful daily deficit without changing what you eat, though eating less fat as well produces far better results.

It stays in your gut

Orlistat is barely absorbed into the bloodstream. It acts entirely within the digestive tract, which is why it has no effect on appetite, mood or energy, and why it does not interact with most other medicines.

How to take Orlistat

When

One 120mg capsule with each main meal, up to three a day. Take it immediately before, during, or up to one hour after the meal.

The rule that saves you trouble

If a meal contains no fat, or you skip a meal, skip that capsule. There is nothing for it to act on, and taking it anyway just increases the chance of side effects from fat later in the day.

Diet alongside it

• Aim for no more than about 30% of your daily calories from fat
• Spread fat evenly across your meals rather than loading it into one
• At roughly 1,800 calories a day, that works out at about 20g of fat per meal
• Check labels, sauces, pastry, cheese and fried food are where fat hides

Vitamins

Take a daily multivitamin containing vitamins A, D, E and K at bedtime, at least two hours after your last orlistat dose. Fat-soluble vitamin absorption is reduced while you are taking it.

Missed dose

If it has been more than an hour since your meal, skip the dose and take the next one with your next meal. Do not double up.

Side effects

Orlistat's side effects are almost entirely digestive and are directly proportional to how much fat you eat. They are unpleasant rather than dangerous, and they are largely within your control.

Very common (more than 1 in 10 people)

• Oily or fatty stools
• Urgent need to open your bowels
• Wind, sometimes with an oily discharge
• Abdominal pain or discomfort
• More frequent bowel movements

Common (up to 1 in 10 people)

• Bowel incontinence
• Bloating
• Tooth or gum problems
• Headache and tiredness
• Irregular periods

Seek medical advice

• Severe or persistent stomach pain
• Yellowing of the skin or eyes, dark urine, itching or unusual tiredness, possible liver problems
• Blood in your stools
• Signs of an allergic reaction

Keeping side effects manageable

The single most effective step is eating less fat. Most people find that side effects settle after the first few weeks as their diet adjusts, the medicine effectively trains you out of high-fat meals.

Ingredients

Active ingredient: orlistat 120mg per capsule.

Other ingredients: microcrystalline cellulose, sodium starch glycolate, povidone, sodium laurilsulfate and talc. The capsule shell contains gelatin, titanium dioxide and indigo carmine.

Supplied as hard capsules in packs of 84 (28 days), 168 (56 days) or 252 (84 days) at three capsules daily.

Important safety information

Do not take Orlistat if you:

• Are pregnant or breastfeeding
• Have chronic malabsorption syndrome
• Have cholestasis
• Are allergic to orlistat or any other ingredient

Speak to your prescriber first if you have kidney disease or a history of kidney stones, type 2 diabetes, or a history of eating disorders.

Medicine interactions: orlistat can reduce absorption of ciclosporin, levothyroxine, amiodarone, antiepileptics and some HIV medicines. It can also affect warfarin control via reduced vitamin K absorption. Separate levothyroxine by at least four hours.

Contraception: severe diarrhoea can reduce the effectiveness of oral contraceptives. Use an additional barrier method if this occurs.

Always read the patient information leaflet supplied with your medicine.