Orlistat blocks about a third of the fat in your food from being absorbed. It works only alongside a reduced-fat diet, and if you do not change what you eat the side effects will make that decision for you.
Take one capsule with each main meal containing fat, or up to an hour after. If a meal has no fat, skip that dose.
The fat you do not absorb leaves in your stool. That is the mechanism, and it is why a high-fat meal produces oily, urgent, hard-to-control stools — the medicine effectively enforces the diet.
Aim for roughly 30% of calories from fat, spread evenly across meals. Fat in one large meal causes more trouble than the same amount spread out.
Alli (60mg) is available from pharmacies for adults with a BMI of 28 or over; the 120mg strength is prescribed.
Orlistat reduces absorption of fat-soluble vitamins A, D, E and K. Take a multivitamin at bedtime, at least two hours away from any orlistat dose.
Expect oily spotting, wind with discharge, urgent bowel movements and oily stools, particularly early on. These reduce as your fat intake falls.
Report severe or persistent abdominal pain, yellowing of the eyes or skin, dark urine, or severe rectal bleeding.
If you have not lost at least 5% of your body weight after 12 weeks, orlistat is unlikely to work for you and should be stopped.
It is not suitable in pregnancy or breastfeeding, or with chronic malabsorption or cholestasis.
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