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The FDA-approved weight loss drug found in Xenical and Alli.

BACKGROUND Start the Diet Now Advertisement

Orlistat is the popular drug, developed by pharmaceutical giant Roche, to treat obesity. Orlistat is probably more recognizable under its marketed names of Xenical or the over-the-counter drug, Alli. Orlistat’s primary objective is to prevent the absorption of fat that is consumed and thereby reduce caloric intake and ultimately body weight.

Orlistat works by inhibiting the pancreatic enzyme, lipase, which is responsible for metabolizing triglycerides in the intestine. Triglycerides are a fancy name for a kind of fat that is found in vegetable oils and animal fats. Without the enzyme lipase, triglycerides are not absorbed and are instead excreted from the body. The prescription form of Orlistat is given to overweight people that also have accompanying conditions of high blood pressure, Type 2 diabetes, high cholesterol or heart diease. Orlistat is also used after weight loss to help people prevent gaining back the weight lost.

There are uncomfortable gastrointestinal side effects that come with taking Orlistat. In addition, Orlistat’s weight loss effects are modest. Those taking Xenical, the prescription form of Orlistat, lost on average about six pounds more than those who just relied on diet and exercise alone during a one-year time frame. Taking the over-the-counter drug Alli results in an average of three pounds greater loss than just relying on diet and exercise alone within a one-year time frame.

  • Taking Orlistat correctly, can reduce weight
  • The FDA has approved Orlistat
  • The active ingredient in FDA-approved Xenical and Alli
  • Published studies proving results
  • Thorough dietary guidance
  • There is no magic pill to weight loss
  • Orlistat has many gastrointestinal side effects
  • Orlistat may not be a long-term weight loss solution
  • Weight loss is modest
  • Must continue to take weight loss medication in order to keep weight off

Orlistat contains a saturated form of lipstatin, a powerful natural inhibitor of lipase, the pancreatic enzyem that absorbs fat.  


Orlistat is taken in a capsule form three times a day with a meal that contains fat. If the meal does not contain fat, then you should not take Orlistat.

At the standard prescription dose of 120mg, three times daily before meals, Orlistat prevents approximately 30% of dietary fat from being absorbed. Over-the-counter dosages, like the product Alli, contain 60mg of Orlistat. This amount prevents about 25% of dietary fat from being absorbed.Taking more Orlistat than the standard 120mg does not accelerate weight loss.


Orlistat is always used in combination with a physician-monitored reduced-calorie and low-fat diet as well as regular exercise program.

You should also not consume foods that contain more than 30% of their calories from fat. This will increase the chances of experiencing gastrointestinal side effects. While taking Orlistat, each meal that you eat should contain 15 grams of fat or less.  It is recommended to eat 2-3 ounces of lean protein with each meal as well as filling your plate with good carbohydrates like vegetables and whole grains. Low-fat or fat-free versions of dairy and salad dressings should be eaten as well as asking for foods to be prepared without fat when dining out.

Since Orlistat also inhibits the absorption of the fat-soluble vitamins, A, D, E and K, a multivitamin that also contains beta-carotene must be taken on a daily basis, preferably at bedtime or two hours after taking Orlistat, to ensure that your body is readily absorbing these necessary nutrients.


Orlistat is one of the only FDA-approved weight loss drugs. Even though it may help those who are overweight or obese to lose weight, it does carry some serious side effects. In addition, those who stop using the drug typically regain the weight back within a few months.

Since Orlistat also contains many contraindications, it is necessary to talk with your doctor before taking any form of Orlistat.

Common Misspellings

Orlystat, Orilistat, Orlastat, Xenical, Zenikal, Ali, Alli,

Related Diets: Alli, Contrave, Xenical

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(Page 1 of 1, 19 total comments)


hi, although orlistat is highly benefical to some, unfortunatly this was not what i exsperienced whilst i was taking orlistat.... i was taking120 mg orlistat 3 times a day & followed the guide lines correctly but i had some very bad side affects, very bad pain in kidney area & liver & feeling very unwell this all followed by a couple of trips to the doctors & blood tests done, i had to stop taking the orlistat straight away & i was pleased to hear from my blood test results that no harm was done to my kidneys / liver & was told by my gp i had a bad reaction to the orlistat, i was still very unwell for a 10 days after i stopped taking the orlistat tablets so it took me a while to recover but am pleased to say am dine now, i thought i would share my own exsperience with you, Although i do no a couple of other people on orlistat who have not suffered the side effects i did & are doing very well with there weight loss, for me its good old heathly eating & plenty of exercise! :)

posted Nov 10th, 2014 3:40 pm


hey there I have just started taking orlistat today. I am a mothe rof 3 children and afte rhaving my first 2 kids I was able to loose 3 and a half stone on my own whilst using weightwatchers, but when I had my last baby who is 16 months old now by c section I could not get the weight to come off.. I went to my doctor and he gave me orlistat I am hoping this will help to give me a kick start .. I never wanted to take diet pills and am very cautious now in taking them. im worried that if the weight comes off and when I stop taking the tablets how do I keep the weight off??

posted Jun 14th, 2013 10:04 am


I have used Alli off and on for a couple of years. When I feel like I am packing on a little weight, I buy a bottle and double the dose to reach prescription strength. I don't experience immediate weight loss, but definitely lose weight over time with this. Yes, there are side effects. Luckily I have a very regular system so my "effects" happen when I expect they will.

There are horror stories all over the Internet. I am sure some people have trouble. However, when I read a story about someone eating half a pizza with an orlistat pill and they express shock over the "outcome" I just have to question if there shouldn't be a minimum IQ requirement to take this drug. I don't monitor my fat intake, but I know better than to take this pill and drink a bottle of Wesson oil. Perhaps weight gain isn't their primary diagnosis and stupidity should be addressed first? I am not perfect, I've overdone the wrong foods with this and experienced what should be isn't as if there aren't warnings. If you make a mistake be cognizant of what may happen and prepare.

If you're looking for this to make you skinny overnight, forget it. If you're using this with a normal diet that would normally NOT cause weight gain, then the calories blocked should result in a net loss. I have had great luck, few issues and am very pleased with this product.

posted Apr 27th, 2013 11:39 am

charlotte d

i started this diet 4 days ago all ready feel less bloated hope to lose a stone or more wish me luck

posted Apr 8th, 2013 11:31 am


i take 1-2 caps when i eat high fat diet.i just had mushroom soup so i had 1 cap. My triglycerides was 275 and it went down to 112 by taking it,although my ldh went up from 120 to 130...i dont know why..i guess i still eat out a lot

posted Mar 17th, 2013 12:01 am


Hi can anyone suggest any foods that I should eat on orlistat as I haven't got a clue and I've been on them now for about 2 weeks and I haven't seen a difference please help

posted Feb 21st, 2013 10:04 am


hi i was on orilstat 5 years ago for about a year and lost 5 stone i kept the weight off for several years but hav gained 2 stone in the last year this is my own fault as i got lax with my diet and intake i have just been back to my gp and gone back on it i know i will see great results as i know how to use it properly i'am sorry if what i'am going to say offends any one but anyone getting constant fatty stools or having leakage needs educating as to how it works the pill doesn't do the work for you you have to work with it and quite frankly anyone having to carry round spare clothes or leaking in bed through the night then complaining it doesn't work shouldn't be on it because if all that doesn't stop you eating chocolate and other junk food nothing will !!!

posted Jan 29th, 2013 6:51 pm

rebekah strachan

i have lost 7lbs in ten days without diet change or exercise. i weighed 20st 6 lbs and i am now 19st 13lbs. the results are remarkable for such a short time period of time. I gained a 8st 4 lbs over the past 18 months due to the medications used to treat my illness and the inability to go outside. I would reccomend orlistat to anyone trying to lose a large amount of wight quickly.

posted Jan 29th, 2013 4:16 am


What effect does Alli have on fat? If I follow a low fat diet and I excercise and I take low calorie, don't I lose weight without alli?? and if Alli stops the absorption of fat, why do i need to cut the fat consumption?

posted Nov 27th, 2011 1:55 pm


I started taking Orlistat after being perscribed my GP back in January of this year. I am extremely overweight BMI was 42, just to give you a rough idea and I'm 5ft 11. My weight has always been difficult to control due to a medical condition which makes exercising very difficult.
Anyway, since taking Orlistat, I have lost 35lb. In just under 5 months. I am happy with this. My weight loss does seem to of slowed recently but I have been experiencing a few other health problems so even the little bit of walking and wii fit exercise i was doing has not been able to happen.
I have never really had any major problems with Orlistat. Yes I some times have the oily stools and orange discharge and yes I do have a tendancy to "fart" on a more regular basis now. The only problem I do suffer from with it is, when you got to go, you GOT to go and this has happened on a couple of occasions when I have not been near a toilet ( usually when walking round a car boot sale in the middle of a muddy field in the middle of nowhere, lol) So there have been a couple of close calls there.
I would recommend it to anyone as long as you follow the guidelines and I find that by drinking a lot of water the side effects are reduced.
It certainly has benefited me and it has helped me with the added incentive of the weight loss meaning i want to carry on and lose even more.

posted Jun 16th, 2011 4:58 am


I think Orlistat (Xenical) is fantastic, I am on the 120mg tablets and have been for 3 months now. In the first two months I lost 1 stone and this month the loss has slowed but that is probably because I have been busy with college work and not had the time to do all my regular exercise. In total I have lost 1stone 3pounds. I don't plan to stay on them for too much longer but I have found them to be very helpful with no side effects at all.

posted Jun 25th, 2010 7:30 pm



posted Jan 22nd, 2010 6:59 am


I took part in a 3-month Obesity/Binge Eating study back in 2004 which included the use of a Placebo or Orlistat (Xenical) conducted by a local Hospital/Medical Center. I would meet with the doctor's weekly and was put on a low-fat diet and asked to do moderate exercise of 30-40 minutes 3 days a week during this study. At the time I was Age 39, 5 ft 7 and 200 lbs. and a cholesterol level of 265 (you had to have a BMI of 30 percent in order to participate in study, and I just made it per the weight and height chart). Half of the study participants were put on a placebo pill and half were put on Orlistat (Xenical). They did not tell the participants during the study which ones they were taking. At the end of the 3 month study, I lost 32 lbs. (down to 168 lbs.) and my cholesterol went from 265 to 199. I was told at that time I was taking Orlistat. The participants who took Orilstat lost more weight than the ones who took placebo and did the low-fat diet. I can only remember once having what may have been an oily stool. I never had cramps, diarrhea or any type of bowel accidents. It is now 2010, and I have put on 20 lbs. since. I am considering trying to get my family doctor to prescribe Orlistat. I have not heard anything negative about the medication, except for the side effects of oily stools, etc. I believe the people who have experienced the bad side effects are people who are continuing to eat fatty foods (such as pizza, cheeseburgers, etc.) and continue to take the Orlistat. If you follow the directions, you are to eat low-fat and also take a multi-vitamin. I look forward to trying out the Orlistat again. :)

posted Jan 13th, 2010 5:23 pm

rachael lowe

i was taking orlistat for 2 years during this time the most i lost was nearing 3 stone but towards the end it was more like slightly over 2 stones. although my eating habits hadnt changed on some weigh in's there was a slight weight gain. i was taken off the pills as a locum doctor decided i had been on them too long and it is possible that taking these kind of pills for longer than is recommended could cause them to start havin the reverse affect. after a lengthy time taking 3 a day i was just stopped. since then i have been in total agony, i am constipated and bloated and the pain i experience when i do get to go to the toilet is eye watering. i am trying to find out if i should have been weaned of them after so long,or if it is safe to just stop. i am going to go back to my gp as i cant continue like this. on the plus side whilst on the pills i didnt suffer side affects,only when i first started going to the toilet was just masses of orange oil but this only lasted about a week. apparently it was pills working against the recent intake of fat i had taken pror to taking the pills.

posted Aug 28th, 2009 4:43 am


I just started using Alli to help with my weight loss/control. I am not overweight but not where I want to be. I have always exercised and counted calories but found my hunger to be the problem. I have lost 5 pounds in 5 months just from exercise and eating about 200 calories less per day. I am very active/fit and find that cutting calories is very difficult for me, so even if Alli does block only 100 calories per day, that will add up to an extra pound per month. It seems if I add fat calories to my total day that will help so Alli will block more. I'm interested to see if this works. Anyone who has feedback please feel free!

posted Feb 9th, 2009 2:35 pm

Jonathan Harrison

If you have tried Orlistat, I would like talk with you about your experience. I'm shooting a documentary analyzing the options out there for weight loss and your story would be very helpful to people. Please contact me . You can see our work online.

Thanks, Jonathan

posted Jan 9th, 2009 5:30 pm


yael, the reason why you are probably having anal discharge is because you are eating things tha t has to much oli in it and that is the way alli or xenical get rid of the fat, by going to the bathroom for number 2. Try to cut a little more of the fat on your meal and you will see results.

posted Nov 18th, 2008 9:53 am


I have been taking Orlistat for a month now and have been pleased with the results. I have lost 11 pounds so far, I probably could have lost more in one month but I have only been exercising 2-3 days a week.

I did not have effects like the other poster. Maybe a little gas, but orange oil wasn't leaking out of me. Honestly, in order to have orange leaking all over your bedsheets and sofa, you are probably eating very fattening, bad foods or not realizing the fat content in the foods you are eating. Remember, this is not a magic pill and you have to carefully monitor your fat intake. I hardly believe someone who calculates their food's fat content carefully will have to wear an adult diaper.

I am very happy with Orlistat and will continue to take until I reach my goal weight.

posted Oct 28th, 2008 11:18 am


I hate this diet!!! I ws on the prescription orlistat... alli is a 50% version of the drug and it made me anal discharge bright orange pure oil.... I had to wear huge overnight pads to keep it from leaking and if it did it stained and ruined everything... (i.e. my sofa, bed linens, undergarments and clothes) I didn't even lose alot of weight... maybe 7 lbs after a few months... I followed all insructions and still the weight loss was nothing as dramatic as the side effects of oily anal discharge ... and NO i could NOT control it..... I do NOT recommend this.....

posted Oct 7th, 2008 1:30 am


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