With over 600 million obese adults currently inhabiting the world, obesity is an epidemic of global proportions. In such circumstances, identifying effective weight-loss treatment strategies is paramount.

A recent comparative analysis, conducted by researchers in London, endeavored to identify the most effective pharmacotherapy for weight loss and found Qsymia to be the most effective weight-loss drug (phentermine-topiramate) among the five major obesity drugs sold in the US, namely liraglutide, orlistat, lorcaserin and naltrexone-bupropion.

According to the  Centers for Disease Control and Prevention (CDC), more than one-third of the US population is obese. Obesity per se is not a disease but is a gateway for a plethora of medical conditions such as heart disease, type 2 diabetes, stroke and cancers.

In addition to being the foundation for other diseases, obesity causes a great deal of financial loss. In 2008, the estimated annual medical cost of obesity in the US alone was $147 billion.

To prevent this, anti-obesity drugs, in conjunction with lifestyle modifications, are the mainstay of obesity treatment. For instance, diet pills control weight by altering processes such as curbing appetite or preventing absorption of calories in the human body.

The main cause of obesity amongst Americans in particular, and the rest of the world in general, is the non-stop consumption of calories, saturated fats, sodium and sugar, and sedentary lifestyle.

Regarding obesity, Tommy Thompson, Former Secretary, US Department of Health and Human Services, says “300,000 American’s die needlessly each year from diseases and healthy conditions related to sedentary lifestyle or poor eating habits.”

The comparative analysis itself, published on June 15th, 2016, in BMJ and JAMA, was a meta-analysis of 28 random clinical trials including a total 29,018 patients on anti-hyperlipidemic or weight-loss therapy. The subjects had an average age of 46 years with a body mass index (BMI) over 36.1.

The review highlighted that about 75% of patients on phentermine-topiramate showed at least 5% weight loss, while, 63% on liraglutide, 55% on naltrexone-bupropion, 49% on lorcaserin, 44% on orlistat and 23% of patients on placebo showed weight loss results during a period of one year. Patients on phentermine-topiramate lost 8.8 kg, while those on liraglutide lost 5.3 kg. Similarly, naltrexone-bupropion administration showed a weight loss of 5.0 kg, while people taking Lorcaserin lost 3.2 kg and those on orlistat lost 2.6 kg.

 “Phentermine-topiramate and liraglutide were associated with the highest odds of achieving at least 5% weight loss,” said Siddharth Singh, MD, MS, Department of Biomedical Informatics, UC San Diego School of Medicine, and the lead author of the study.

All of the five aforementioned drugs are approved for long-term use in treatment of obese or overweight people by the Food and Drug Administration (FDA).

However, researchers did state that there are certain limitations to their results since there was a ‘shortage of direct comparative studies’ and all the trials assessed had a high attrition rate of 30-45% meaning the evidence does not have a strong foundation.

The drug found most effective in anti-obesity treatment, Qsymia, is a blend of two drugs called Phentermine and Topiramate. Its effectiveness can be attributed to the unique combination of the two drugs present in it. For instance, Phentermine is an appetite suppressant, while Topiramate, is used for treatment of epilepsy and migraines. Both work in combination to suppress hunger. Qsymia pills are prescribed as once per day and are available in three dosages; low (3.75 mg phentermine/23 mg topiramate), moderate (7.5 mg P/46 mg T) and a high (15 mg P /92 mg T).

Janet Woodcock, MD, Director of the FDA’s Center for Drug Evaluation and Research, believes that if used responsibly and with a healthy lifestyle, Qsymia provides another treatment option for chronic weight management in obese Americans.

After Qsymia, the drug Saxenda was found to be the most effective, while the drug, Xenical, showed the lowest likelihood of losing weight. On the other hand, Saxenda (liraglutide) and Contrave (naltrexone-bupropion) were found to cause the most adverse effects in patients and accounted for higher rates of discontinuaton, while Belviq (Lorcaserin) and Xenical (orlistat) were found to have the lowest rates of adverse effects.

It should also be noted that only Xenical in the UK has been approved by the National Health Services (NHS) and is currently available in the UK market market. The drug Saxenda has also been approved by the European Medicines Agency, but is yet to be launched in the UK.

The most successful weight-loss treatments entail setting goals and incorporating lifestyle changes, such as being physically active and consuming fewer calories. Diet pills and weight-loss surgery, called bariatric surgery, should be the last resort for people who cannot effectively manage their weight despite efforts and lifestyle alternations.

The first prescription obesity medication in the US, methamphetamine, was approved and launched in 1947. However, in 1973, the FDA limited the availability of such drugs in the market over adverse health concerns. After a ban of 13 years, the FDA finally started approving drugs for weight loss management.

Approved by the FDA in July 2012 both for obese adults with a BMI over 30 and for overweight adults with a BMI greater than 27 who are suffering from at least one weight-related condition such as diabetes or hypertension, Qsymia was also one of the first drugs to be approved as a life-long therapy for battling obesity.

Previously, only Orlistat (Saxenda) was available as a long term anti-obesity drug but in a limited capacity only. Furthermore, lower doses of Orlistat are sold in the US under the name of Alli.