Orlistat How Does It Work?

orlistat-120mg-84-tablets_4Orlistat, also known as tetrahydrolipstatin, is a common drug used in the treatment of obesity. It is sold under the brand name Xenical which is manufactured by Roche in most countries. In the United Kingdom and the United States, it is also sold over the counter in many Pharmacies at a lower dose via a product called Alli, which is produced by GlaxoSmithKline. Its primary function is in preventing the absorption of fats from our diets as food passes along the intestine, which, therefore, reduces our calorific intake. This medication is recommended to be used in conjunction with a reduced calorie diet and exercise programme supervised by a healthcare provider. Orlistat is available as an oral capsule at two strengths or 120mg or 60mg and is coloured dark blue.

100x90Orlistat can be provided both on prescription following a consultation with a healthcare professional, such as a doctor or a nurse, or an online doctor service like Assured Pharmacy, or alternatively, in a pharmacy as an over-the-counter sale after a brief consultation with a pharmacist to assess suitability.

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Orlistat’s mechanism of action works by a process known as local lipase inhibition. This means the drug Orlistat works by stopping enzymes known as lipases in the stomach and pancreas from breaking down fats known as triglycerides. Stopping these lipase enzymes the triglycerides, which are high in level after eating fatty foods, cannot be broken down into fatty acids. This conversion is an essential step in the absorption of fat which involves a hydrolysis reaction. As the triglycerides are not broken down to fatty acids, the triglycerides cannot, therefore, be absorbed in the intestine and are subsequently excreted in our bowel movements. The net effect of is, simply, that the fat in foods cannot be taken into the body but are rather excreted undigested. The main route of elimination is through the passing of faeces. Based on samples of fat measurements in faeces, the effect of Orlistat can be seen as soon as 24 to 48 hours after taking a dose. Further to this, after stopping Orlistat fat measurements in faecal matter returns to normal in as little as 48 to 72 hours.

So who is it for? Orlistat is recommended, alongside a calorie-controlled diet, for obesity management including weight loss and weight maintenance. Further to this, someone who would be classified as obese would have an initial BMI of 30kg/m2 or more. BMI can be calculated by dividing a person’s weight in kilograms by their height in meters squared. There are tools online which can calculate this for you, as well as self-weigh machines which can provide this information. These machines are available in most pharmacies. Orlistat can also be indicated for BMI’s of 27kg/m2 or more, in cases where the patient has other conditions such as hypertension or diabetes. Your healthcare provider will be able to help you in making whether Orlistat is suitable or not for you.

Indeed, it should be noted by patients, that not everyone is suitable for this medication and its supply will be subject to the discretion of health care professionals following a discussion with the patient to assess the suitability of the supply.



Orlistat has been proven to help patients lose weight in clinical trials. Orlistat is the generic, non-branded form of Xenical, and is therefore better value for money. Both medicines have exactly the same effectiveness.

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What Is Orlistat?

Orlistat can be used to help with weight loss. Rather than being an appetite suppressant it stops your body from absorbing the fat from food. This process helps the body to lose weight. Orlistat is not a single solution and should be used with a sensible calorie controlled diet.

Orlistat blocks approximately 1/3 of the fat from your food by attaching to enzymes in the digestive system and stopping them from breaking down the fat content of your food. The undigested fat is simply passed through your system.

How to Take Orlistat

The recommended dose of Orlistat is a 120-mg capsule taken with water with each meal that contains fat. You should take Orlistat up to three times a day in conjunction with a reduced-calorie diet. Each time you take Orlistat , your nutritionally balanced meal should contain no more than about 30% of calories from fat.

You should evenly divide your daily intake of fat, carbohydrates and protein over three main meals. Take Orlistat during meals or up to 1 hour after a meal. If you occasionally miss a meal or have a meal without fat, you can omit your dose of Orlistat . Doses above 120 mg three times daily have not been shown to provide an additional weight-loss benefit.

You should try to follow a healthy eating plan, such as one from which no more than 30% of calories come from fat. Following this eating plan will help you lose weight while decreasing some of the possible gastrointestinal effects you may experience while taking Orlistat . You may also need to adjust your calorie intake and/or your activity level, including reasonable exercise.

If your meal contains too much fat, you may experience diarrhoea. In the case of bloody stools, discontinue use and seek medical advice.

Vitamin Supplements

Because Orlistat interferes with your body’s absorption of some fat-soluble vitamins, you should take a daily multivitamin supplement that contains vitamins A, D, E and K and beta carotene once a day at least 2 hours before or after taking Orlistat , such as at bedtime

Patient Information Leaflet

Always read the patient information leaflet before commencing treatment. Patient information can be found here.


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The typical dose of the medication is 120mg (when given via a prescription consultation) or 60mg (available OTC in a registered pharmacy) three times a day prior to eating or up to one hour after a meal. It has been found in studies that doses greater than 120mg three times a day have no additional weight loss benefit. In addition, manufactures of Orlistat recommend that each time you take this medication the meal taken in contains no more than about 30% of its calories content from fat. Therefore, in relation to this, if you miss a meal or have a meal without fat you can omit the dose of Orlistat.

The typical prescription strength dose of 120mg three times a day should, on average, stop the absorption of around 30% of dietary fat, whereas,  the over-the-counter dose as available in pharmacies is 60mg three times a day prior to meals would prevent the absorption of approximately 25% of dietary fats. Indeed, with results like this, it is clear to see why profits of Orlistat are booming.

Indeed, Currently 64% of adults in the UK are overweight or obese and this figure is set to increase.
Furthermore, between 1980 and 2008 the number of overweight adults has increased from 23% to 34%.
This is problematic for many obvious reasons such as the knowledge that excess weight contributes to the development of many medical problems such as high blood pressure, high cholesterol, heart disease and diabetes.
In relation to how Orlistat can help in reducing a person’s weight is in reducing the amount of dietary fat. This is because the consumption of excess fatty food and calories plays a major role in a person gaining weight. Fat provides twice as many calories per gram of weight as carbohydrates and protein.

Viagra Side EffectsBut what’s the drawback? For many patients, it can be the side effects, especially in relation to changes in bowel movements. This is generally unsurprising considering its mechanism of action, as discussed earlier. Many patients’ movements change in terms of frequent oily spotting, increased urgency and frequency of bowel movements and inability to control bowel movements. Furthermore, due to the presence of undigested fat, the oil seen in a bowel movement may be clear or have an orange/brown colour. These differences are natural and indicate that the product is working.  These changes generally occur during the first weeks of treatment but can continue throughout the use of Orlistat. The severity can be intensified following the consumption of meals which are higher than the recommended amount of 30% in content. Side effects in adults and adolescents were reported to be similar. If you are taking Orlistat and you are concerned about side effects you may be experiencing, talk to your Pharmacist or Doctor.

As mentioned, it is recommended that Orlistat is used in conjunction with other measures including diet changes and exercise. These changes should ideally be initiated prior to starting treatment and be continued after discontinuation of Orlistat. Typical advice which would be given in terms of a patient’s diet would include reducing the portion size, the amount of unnecessary snacking and increasing the amount of fruit and vegetables. Furthermore, daily intake of calories should be over three meals, none of which should have a fat content greater than 30%; so for a 2000 kcal a day diet, which would be typical for women, would have approximately 67g of fat. Diet changes like these, in combination with an exercise programme, are recommended for the best possible results. Before commencing any exercise programme it is important to first consult your healthcare professional.

In terms of efficacy, trials show that there is a benefit in using Orlistat. Indeed, following one year of treatment, Orlistat in combination with diet and other lifestyle modifications was shown to be more effective in reducing weight than diet alone. In most cases, weight loss was gradual. Patients treated with Orlistat and a reduced-calorie diet for one year lost an average of 13.4 pounds while those on a reduced-calorie diet alone lost 5.8 pounds.
Similarly, in adolescent users, following one year of treatment, Orlistat in combination with similar lifestyle changes was shown to be more effective in reducing Body Mass Index (BMI) than diet alone. Further to this, a reduction in Body Mass Index is a better indicator of weight loss in children because it takes into account changes in weight related to growing children.

Therefore, in conclusion, Orlistat can be a very useful drug in the above-mentioned indications. It should be used alongside other changes to achieve the best and most sustainable changes which can help people gain long-term health benefits. In addition, it should be used in supervision with a healthcare professional to ensure patient safety at all times.

If you are interested in trying Orlistat and would like to see if you are suitable to take it, contact your doctor, pharmacist or other healthcare professional for the best advice available.


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Assured Pharmacy is not liable for the currency or accuracy of the information contained in this blog post. For specific information about your personal medical condition, please contact our doctors or pharmacists for advice on [email protected].