Home » Orlistat Review: Can You Achieve A Weight Loss?

Orlistat Review: Can You Achieve A Weight Loss?

Orlistat review of effectiveness

As many of us are aware, losing weight can be difficult. Intake of dietary fat (‘bad fat’) can significantly increase calorie intake and contribute to overall obesity.

Orlistat is one of two drugs available in the UK for the management of obesity. Orlistat stops the absorption of fats in the body, causing weight loss.

The following main areas will be covered by the Orlistat review:

  • Orlistat (P) and Orlistat (POM) what is the difference?
  • Who can buy Orlistat?
  • Orlistat review of mechanism of action
  • Can you get Orlistat on the NHS?
  • Orlistat review of the effectiveness
  • Orlistat review of side effects
  • Drug interactions

Orlistat (P) And Orlistat (POM) What Is The Difference?

Orlistat has been available on the market since 1999 as a prescription-only medication. As with many drugs, initially, Orlistat was only available as one branded product called Xenical (120mg of Orlistat), until the expiry of ‘exclusivity’ rights (patent) in 2009. Today Orlistat is available as a generic medication produced by a number of drug companies.

In 2009 Orlistat became available as pharmacy-only medicine (P), known as Alli for sale to the public, without a prescription. Alli can be purchased from a chemist under the supervision of a pharmacist or online from registered pharmacies.

Each capsule of over-the-counter Alli contains 60mg of Orlistat. In contrast, each capsule of prescription-only Orlistat contains 120mg of Orlistat. Both Alli and Orlistat (POM) are indicated for the treatment of obesity in conjunction with a mild-low calorie and fat diet.

Who Can Buy Alli (Orlistat)?

Over-the-counter Alli can be used by adults (18 years or over) who are overweight with a body mass index (BMI) of 28 kg/m2. Although there is no specific direction to measure a patient's BMI when a purchase request is made at the conventional pharmacy, customers may be asked to have their BMI checked (weight and height measurement). Online pharmacies have a more relaxed approach to the sale of Alli.

Who Can Buy Alli

When purchasing Alli online, customers may need to read and agree with a disclaimer confirming the suitability of the drug or answer pre-sale questions; for example, you may be asked to provide your weight and high (to calculate BMI) and detail any other conditions you may have.

Orlistat Review Of Mechanism Of Action

Orlistat stops the production of certain substances in the body, which are responsible for breaking down fats in the intestine. As a result, these fats are not absorbed by the body and are removed mainly through feces. It is estimated that Orlistat blocks the absorption of about 25% of fat that is being consumed.

How To Take Orlistat?

  • Alli: one 60mg capsule is taken three times a day which each meal that contains fat. No more than three capsules should be taken in 24 hours
  • Orlistat: one 120mg capsule is taken three times a day, also with a meal that contains fat

How To Take Orlistat


Orlistat should be taken just before, during, or up to one hour after a meal. Orlistat should not be taken when a meal is missed or does not contain fat. Patients are recommended to take a multivitamin containing fat-soluble vitamins (A, D, E, and K) at night before going to bed.

Can You Get Orlistat On NHS?

Orlistat can be prescribed by a GP. Last year (Oct’ 18—Sep ’19), almost 360000 prescriptions were issued for Orlistat (OpenPrescribing.net, 2019).

Prescription-only Orlistat is indicated for the management of obese patients with a body mass index (BMI) greater or equal to 30 and where diet and exercise have been evaluated or overweight patients with BMI greater of or equal to 28 with existing risk factors such (NICE, 2017):


  • As type 2 diabetes,
  • High blood pressure
  • High cholesterol /fats level

Can You Get Orlistat On NHS

Orlistat will be re-prescribed only if 5% or more of body weight loss is achieved within 12 weeks of the start of treatment; however, different goals may be set for certain patients, for example, type 2 diabetic patients (ibid).

Orlistat Review Of Possible Side Effects

The most common side effects of Orlistat treatment are gastro-intestinal (GI) side effects. These include:

  • Oily discharge from the rectum
  • The urgency to go to the toilet
  • Oily/Fatty/Liquid stools
  • Flatulence (excess of gas)
  • Abdominal pain and discomfort

GI side effects are largely related to how much fat is consumed by a patient, which can be explained by Orlistat’s mechanism of action (see the previous paragraph).

Increased intake of fat means more fat is being excreted through the feces. It is essential that patients follow a low-fat diet during the treatment with Orlistat. This not only reduces the likelihood of GI side effects but also helps you to achieve a more significant weight loss.

Importantly almost 50% of patients who take Orlistat/Alli will not experience GI side effects related to a diet (myalli.com, N.D.). Lack of side effects does not mean Orlistat is not working.

Other common side effects associated with the use of Orlistat during clinical trials include:

  • Influenza
  • Hypoglycemia (low sugar level)
  • Headaches
  • Upper respiratory infections (colds)

Read product information leaflet (PIL) for a list of all possible side effects. PIL can be accessed online.

Orlistat Foods To Avoid

The idea is simple: avoid fats. There are thousands (if not millions) of websites, blogs, useful books, diet plans, and recipes that focus on healthy eating. Follow a low-fat, reduced-calorie diet. Some ideas for a low-fat diet:

  • Aim for meals with fat-derived calories of around 30% (15 grams of fat) per meal
  • Reduce/avoid the use of oils in cooking
  • Use low-fat spreads instead of butter
  • Focus on eating 'low-fat range' of products, for example, low-fat cheese, light or fat-free cream cheese, low fat/fat-free yogurts, and so on
  • Avoid 'take outs' and deep-fried foods like chips
  • Eat lean cuts of skin free meat

Orlistat review of weight loss pill

Orlistat Review Of Clinical Effectiveness: Can You Lose Weight With Orlistat?

Orlistat was well studied in human trials. The next couple of paragraphs summarise the main outcome of clinical trials for Orlistat and Alli, focusing on the effectiveness of weight loss (EMA, 2009 & EMA, 2008).

Xenical studies (Orlistat 120mg taken three times a day)

  • Seven main studies, which included over 3000 obese patients
  • Duration: one to four years
  • Placebo-controlled: some patients were given a ‘dummy’ pill
  • Xenical (120mg) or placebo were given three times a day to patients in conjunction with dieting (hypocaloric, low-fat diet)
  • Results: After one year patients on Xenical lost an average of 6.1kg of body weight compared to 2.6kg who took a dummy pill
  • 20% of patients who took Orlistat lost more than 10% of their body weight as compared to 8% of patients who took a dummy pill
  • At the end of the four-year study, 21% of patients lost over 10% of body weight as compared to 10% of patients who took a placebo

Alli studies (60mg of Orlistat)

  • Two main studies
  • Duration: 12 months
  • Placebo-controlled: Orlistat 60mg three times a day or placebo pill were taken by participants alongside hypocaloric, low-fat diet
  • Most weight losses occurred during the first six months of the trial
  • At six months average weight loss with Alli was 5.20kg compared to 3.1kg with placebo (study 1) and 3.6kg versus 1kg (study 2) with an overall average weight loss of 4.4kg when Alli was taken compared to 2.1kg when a dummy pill was taken (both studies)
  • At 6 months, over 16% of participates lost 10% or more of their body weight as compared to 6.5% for placebo

Interestingly, the data from the above studies showed improvements in cholesterol levels which decreased after 6 months of treatment:

  • Total cholesterol decreased by 2.4%
  • LDL ‘bad’ cholesterol decreased by 3.5%
  • Patients taking a placebo experienced an increase in cholesterol level

Alli also had a positive effect on waist circumstance, which decreased after six months. Overall, both Orlistat 120mg and Alli (60mg of Orlistat) showed a significant reduction in body weight as compared to the placebo.

Orlistat Review Of Drug Interactions

Please refer to the product information leaflet for a full explanation of the possible interactions of Orlistat. The following drug interactions are listed in Orlistat’s specifications:

  • Amiodarone (used in the treatment of ventricular fibrillation): in a healthy volunteer, some decrease of levels of amiodarone was observed
  • Ciclosporin (immunosuppressive medication): it is not recommended to use Orlistat whilst on ciclosporin as plasma levels of ciclosporin may be affected
  • Acarbose (used in treatment in alcohol dependence): concomitant use should be avoided
  • Oral anticoagulants (for example, warfarin): use of Alli together whilst on anticoagulants are contraindicated, however when prescribed, Orlistat can be considered, providing an international normalized ratio (INR) is monitored
  • Fat-soluble vitamins (A, D, E, K): the majority of patients taking Orlistat during a four-year study had no change in levels of vitamins A, D, E, and K, however, manufacturers of Orlistat recommend taking a multivitamin supplement at bedtime
  • Possible interaction with antiretroviral medicinal products for HIV

Orlistat interaction with oral contraceptives:

There is no direct interaction between Orlistat and oral contraceptive drugs; however, manufactures of Orlistat recommend using additional contraceptive if severe diarrhea is experienced by patients.

In 2010, MHRA issued a safety update in relation to possible interactions with Orlistat:

  • Levothyroxine:
  • Decreased absorption of iodine salts or levothyroxine (or both) may cause reduced control of hypothyroidism or cause (rarely) hypothyroidism
  • Patients are advised to speak to their doctor before taking Orlista
  • Antiepileptic drugs:
  • Orlistat may affect the absorption of antiepileptic medication such as lamotrigine or sodium valproate, causing a lack of seizure control

Always read the product information leaflet before starting any treatment or speak to your GP or pharmacist.

Orlistat Alternative Drugs

At this time in the UK, there are only two drugs licensed for weight loss, the first of which is Orlistat. Second, Liraglutide, known under its branded name as Saxenda. Saxenda works in a different way from Orlistat. Read more about Saxanda in my separate post: Saxenda review – effectiveness of NEW weight loss drug.

Orlistat review summary

Results from clinical trials for Orlistat and Alli clearly show benefits in weight reduction as compared to placebo. One needs to remember that Orlistat was used in conjunction with diet.

Orlistat is not a ‘magic bullet’ for weight loss. Patients taking Orlistat must be taken in conjunction with a hypocaloric diet. I will leave you with what I thought: what would combine Orlistat with diet and exercise achieve?


What is your experience with Orlistat? Please leave a reply and share this post.


  1. McNeely, W. and Benfield, P., 1998. Orlistat. Drugs56(2), pp.241-9. Available at https://europepmc.org/article/med/9711448 – accessed on December 09, 2019.
  2.  Gervasoni, C., Cattaneo, D., Di Cristo, V., Castoldi, S., Gervasi, E., Clementi, E. and Riva, A., 2016. Orlistat:      weight lost at cost of HIV rebound. Journal of Antimicrobial Chemotherapy71(6), pp.1739-1741. Available at https://academic.oup.com/jac/article-abstract/71/6/1739/1751634 -accessed on December 10, 2019.