Which Weight Loss Pill is Most Effective?

Finding out which weight loss drug is right for you can be a real struggle, with each brand claiming to have the most effective weight loss medication, it can be difficult to know which one to choose. This is why we’ve created an unbiased comparison of 7 leading weight loss products, in order to provide you with the information you need before deciding which treatment is best for you.

In this article, we compare some of the most popular weight loss drugs: Alli, Diethylpropion, Mysimba, Orlistat (Xenical), Phentermine, Saxenda and Xenical (Orlistat). We discuss the similarities and differences between these types of weight loss medications in order to help you to find the best weight loss medication that suits you.

The tables below outline some key information about each weight loss drug, including their forms, active ingredients, how they work, common side effects, prices, availability on the NHS and recommended users.  

 

Alli Diethylpropion Mysimba Orlistat (Xenical)
Form Capsule Tablet & Capsule Tablet Capsule
Active ingredient Orlistat Diethylpropion Hydrochloride BP Naltrexone Hydrochloride and Bupropion Hydrochloride Orlistat
How it works Stops around a quarter of the fat in food from being absorbed into your system Suppresses appetite & helps you to feel fuller for longer Changes feelings about foods & takes some pleasure away from eating Stops a third of the fat in food from being absorbed into your system
Common side effects Wind (flatulence) with or without oily spotting, sudden bowel motions, fatty or oily stools Nausea, vomiting, diarrhoea, upset stomach, constipation;

headache, blurred vision;

sleep problems,

dizziness, drowsiness,

depressed mood,

dry mouth, unpleasant taste in the mouth,

decreased sex drive, redness, bruising, or rash.

Feeling sick (nausea), being sick (vomiting), pain in the abdomen, constipation, headache, difficulty sleeping (do not take Mysimba near to bedtime), anxiety, agitation, joint and muscle pain Headache, abdominal pain/discomfort, urgent or increased need to open the bowels, flatulence (wind) with or without discharge, oily discharge, oily or fatty stools, liquid stools, low blood sugar levels (experienced by some people with type 2 diabetes), upper respiratory infections, flu (influenza)
Price for a 1-month course

(31 days)

£38.74 £124.46 £35.98
Available on NHS
Intended user People with a BMI ≥28 People with a BMI ≥30 who have not responded to diet and exercise alone People with a BMI >30 People with a BMI >30

 

Phentermine Saxenda Xenical (Orlistat
Form Capsule Injection Capsule
Active ingredient Phentermine Liraglutide Orlistat
How it works Suppresses appetite & helps you to feel fuller for longer Suppresses appetite & helps you to feel fuller for longer Stops a third of the fat in food from being absorbed into your system
Common side effects Itching,
dizziness,
headache,
dry mouth,
unpleasant taste in the mouth,
diarrhoea,
constipation,
stomach pain,
increased or decreased interest in sex.
Feeling sick (nausea),
being sick (vomiting),
diarrhoea,
constipation
Headache,
abdominal pain/discomfort,
urgent or increased need to open the bowels,
flatulence (wind) with discharge,
oily discharge,
oily or fatty stools,
liquid stools,
low blood sugar levels (experienced by some people with type 2 diabetes)
£217.21*

*price based on the 3x3mg deal

£55.35
Available on NHS
Intended user People with a BMI ≥30 People with a BMI >27 People with a BMI >30

 

Effectiveness is one of the most important considerations to bear in mind when trying to decide which weight loss medication is right for you. The table below reports the findings of scientific studies that have been conducted on each of these weight loss products to help you discover which weight loss pill is most effective.

 

Medication Effectiveness
Ali A research study found Orlistat (the active ingredient in Alli) to be an effective anti-obesity drug. Participants taking Orlistat for 24 weeks lost an average of 4.65kg, which was significantly more than those taking the placebo, who lost an average of 2.5kg.
Diethylpropion A study of 50 patients from a private practice found that during a 12 week period, participants taking Diethylpropion lost an average of 14.8lb, which is 5.8lb more on average than those who took the placebo
Mysimba A meta-analysis of Mysimba trials has found that in 3 studies, participants’ weights were reduced by 3.7% to 5.7%, which is much greater than that of the placebo, which only reduced patients’ body weights by 1.3% to 1.9%.
Orlistat (Xenical) A research study proved Orlistat to be an effective anti-obesity drug. The participants who took Orlistat for 24 weeks had an average weight loss of 4.65kg. This was much greater than the average weight loss observed in participants who took the placebo, which was an average of 2.5kg.
Phentermine A meta-analysis of 6 studies found that obese patients taking Phentermine lost an average of 6.3kg, which is 3.6kg more than those who took the placebo.
Saxenda After a 56-week trial, participants using Saxenda lost an average of 17.3lb, which was over twice as much as those taking the placebo, who lost an average of 7lb.
Xenical (Orlistat) A study found that Orlistat (the active ingredient in Xenical) is an effective anti-obesity drug. The participants who took Orlistat for 24 weeks lost an average of 4.65kg. During the same time frame, participants taking the placebo lost only 2.5kg, which was significantly less than those taking Orlistat.

 

*These reports are all based on results from studies where the weight loss medications were taken as directed. The participants involved in many of these studies were instructed to reduce their daily calorie intake, limit the amount of fat in their diets, participate in exercise and in some cases, take part in counselling alongside taking the medication.

Alli

Alli is an FDA-approved weight loss supplement widely used in the UK to help patients to lose weight and lower their BMI. The active substance in Alli is Orlistat which helps to treat obesity by reducing the amount of fat that your body can absorb. The drug stops around a quarter of the fat in foods consumed from being absorbed into your system.

Alli comes in capsule form and should be swallowed whole with water. Some of the most common side effects of Alli include wind (flatulence) with or without oily spotting, sudden bowel motions and fatty or oily stools. A full list of side effects can be found in the Alli patient information leaflet.

The price for a 1-month course of Alli costs just £38.74, making it one of the most affordable weight loss pills in this comparison. The average user rating for this medication on the online pharmaceutical encyclopedia drugs.com is 6.1 out of 10.

Diethylpropion

Diethylpropion is an appetite suppressant recommended for short-term use to help patients to manage their obesity. It contains the active ingredient Diethylpropion Hydrochloride BP, which works by stimulating your central nervous system, causing a rise in your blood pressure and heart rate which in turn decreases your appetite.

The drug is available in both tablet and capsule form and should be swallowed whole with some water. Common side effects of Diethylpropion are; nausea, vomiting, diarrhoea, upset stomach, constipation, headache, blurred vision, sleep problems, dizziness, drowsiness, depressed mood, dry mouth, unpleasant taste in the mouth, decreased sex drive, redness, bruising, or a rash.

Diethylpropion is a controlled substance. It has some chemical and pharmacologic similarities to stimulant drugs such as amphetamines, which are known for being misused. A face-to-face consultation is often required in order to get Diethylpropion on prescription.

Mysimba

Mysimba is approved for use in the EU by the Committee for Medicinal Products for Human Use (CHMP) as an effective medication for weight loss. The exact way that Mysimba works are not yet fully understood, however, it’s thought that the combination of the two active ingredients work together in order to change the way we think and feel about food.

This medication comes in tablet form, which should be swallowed whole with some water.  Mysimba’s side effects include feeling sick (nausea), being sick (vomiting), pain in the abdomen, constipation, headache, difficulty sleeping (do not take Mysimba near to bedtime), anxiety, agitation, joint and muscle pain. A full list of side effects can be found in the Mysimba patient information leaflet.

A 1-month course of Mysimba costs £124.46, with user reviews on drugs.com rating its efficacy at 6.9 out of 10.

Orlistat (Xenical)

Orlistat is a gastrointestinal lipase inhibitor. When taken, it decreases the amount of fat your body is able to absorb, and therefore reduces calorie intake enabling users to lose weight.

Orlistat comes in capsule form and should be swallowed whole with water. The following side effects are frequently observed in patients taking this medication: headache, abdominal pain/discomfort, urgent or increased need to open the bowels, flatulence (wind) with or without discharge, oily discharge, oily or fatty stools, liquid stools, low blood sugar levels (experienced by some people with type 2 diabetes), upper respiratory infections and flu (influenza). For a full list of side effects please see the Orlistat patient information leaflet.

A 1-month course of this medication costs £35.98, making it the most affordable weight loss treatment in this comparison. The average user rating of Orlistat is 7.5 out of 10.

Phentermine

This medication contains the active substance Phentermine, which helps users to lose weight by suppressing their appetites, helping them to feel fuller for longer. The exact way these medications works is not fully understood. However, it’s theorized that Phentermine works by increasing the neurotransmitter levels in the brain, which in turn stops the hunger signal, tricking the brain into thinking that the body is not as hungry.

Phentermine comes in capsules, which should be swallowed whole with some water. Common side effects associated with this drug include itching, dizziness, headache, dry mouth, an unpleasant taste in the mouth, diarrhoea, constipation, stomach pain, increased or decreased interest in sex.

Saxenda

Saxenda is an appetite suppressant containing the active ingredient Liraglutide. It works by mimicking the GLP-1 hormone, which tells the brain when the body is full. This process helps users to feel fuller for longer, meaning that we eat less and therefore lose weight over time.

This medication comes in the form of an injection, which patients are directed to administer themselves. The full instructions including how and when to inject this medication can be found in the Saxenda patient information leaflet. A full list of side effects associated with this drug can also be found in the patient information leaflet, with some of the most common beings: feeling sick (nausea), being sick (vomiting), diarrhoea and constipation.

A 1-month course of Saxenda costs £217.21*. The medication has a user rating on drugs.com of 7.8 out of 10.

Xenical (Orlistat)

Xenical is a branded version of the generic drug Orlistat. It contains the active ingredient Orlistat which is a gastrointestinal lipase inhibitor. The medication works by reducing the amount of fat that the body is able to absorb and therefore helps patients to lose weight.

This drug comes in capsule form and should be swallowed whole with water. Common side effects of Xenical include headache, abdominal pain/discomfort, urgent or increased need to open the bowels, flatulence (wind) with discharge, oily discharge, oily or fatty stools, liquid stools and low blood sugar levels (experienced by some people with type 2 diabetes). The Xenical patient information leaflet contains a full list of side effects.

Users have rated Xenical 8.3 out of 10 for efficiency on the site drugs.com. Although Xenical contains the same active ingredient as Orlistat and works in the same way, Xenical is more expensive as it’s the branded version of the drug. 1 month of Xenical costs £55.35.

We hope this comparison of weight loss medications has been useful in providing you with an overview of some of the most popular weight loss drugs available. It’s important to bear in mind that these weight loss products only work if they’re used as directed, (often alongside dietary altercations and exercise). Before starting any new medication, it’s vital that you speak to a GP first.