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Weight Loss Medications: What You Need to Know

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Maria Jacob

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Thursday, January 18, 2024

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Weight loss medication is needed by people who are suffering from obesity and have a BMI of ≥27~30 kg/m2 with major health concerns like cardiovascular disease, hypertension, and high cholesterol. 

The most common prescription weight loss drugs regulated by the US FDA include Bupropion-naltrexone (Contrave), Tirzepatide (Zepbound), Liraglutide (Saxenda), Orlistat (Xenical, Alli), Phentermine-topiramate (Qsymia), Semaglutide (Wegovy), and Setmelanotide (Imcivree).

Weight loss drugs are part of a weight loss program that includes improved nutrition, regular physical activity, and a regulated sleep pattern. These weight loss pills are not a substitute for healthy habits (diet and exercise) by any means.

Do You Need Weight Loss Medication?

Obesity is a growing global concern, with two-thirds of the United States population reporting to be overweight or obese in 2015. (1) Not only this, a 2017 study by the name Global Burden of Disease (GBD) showed that a body mass index (BMI) ≥25 kg/m2 was associated with 2.4 and 2.3 million deaths in women and men, respectively, which is alarming. (2)

Obesity and overweight issues are one of the major risk factors for heart disease, stroke, prediabetes, and diabetes. The most risk-prone population are those with a BMI ≥27~30 kg/m2 wherein obesity can prove to be fatal. (2) Weight loss is a primary goal for obese and overweight people. People with type 2 diabetes, high blood pressure, or/and high cholesterol, with a higher BMI, are also given a weight loss prescription due to impending risk factors. (3) (4)

However, to say that everyone who is overweight needs weight loss pills would be wrong. Obesity itself is a multifactorial condition where diet, sleep patterns, physical activity, genetics, and environmental factors also play significant roles. Hence, one can always adapt significant lifestyle, behavioural, and dietary changes to move to a healthy weight.  However, there are medications to treat people affected by obesity as a chronic, metabolic disorder. (5

There Are FDA-Approved Prescription Weight Loss Drugs: Please Do Not Fall For Marketing Traps and Online Weight Loss Doctors!

The most common prescription weight loss drugs approved by the US FDA include Bupropion-naltrexone, Liraglutide, Orlistat, Phentermine-topiramate, Semaglutide, and Setmelanotide. The US FDA recently approved Tirzepatide for weight loss in addition to a calorie-deficit diet and physical activity.

As per the recent guidelines released by the American Gastroenterological Association, the first-line drugs to be used for long-term treatment of obesity include semaglutide, liraglutide, phentermine-topiramate extended-release (ER), and naltrexone-bupropion ER, based on moderate-certainty evidence.(6

Besides, a biodegradable, oral non-systemic super absorbent hydrogel (Plenity) is also recommended by the FDA as a weight loss pill. It is made from cross-linked carboxymethylcellulose and citric acid and works by enhancing satiety and fullness. (6) (7

There are plenty of weight loss ‘supplements’ containing herbs, high-fiber components, multivitamins, diuretics, laxatives, and minerals available in the market and as a part of weight loss medication online. They claim to promote weight loss, increase fat burning and enhance overall wellness. 

As promising as these avenues might look like to the consumer, there is little scientific evidence of such supplements providing any benefit. Some of these compounds may even be plant-based and marketed as ‘natural’ products. However one should only resort to any form of supplement after consulting with their nutritionists or specialists.(8) (9) (10)

The Science Behind Weight Loss Medication: How Do They Work?

Weight loss pills work in different ways. Some can make one feel full more often or reduce the appetite so that one is not frequently hungry. Some weight loss medication makes absorption of fats difficult from food because of which one does not gain more weight, while the others increase the rate at which calories are burnt.

Naltrexone and Bupropion are used to treat alcohol and opioid addiction and anti-depressants respectively, post the FDA’s approval. However, this combination is also believed to work synergistically in the hypothalamus and the mesolimbic dopamine circuit (a central nervous system pathway) to make people feel fuller faster, reduce food intake, and increase calorie burning. (11) This led to FDA eventually approving this combination for prescription weight loss medication. However, there is a risk of increased blood pressure when using this drug combination and hence it should only be taken under a legally prescribed regimen. 

Orlistat prevents the absorption of dietary fats by blocking the gastric and pancreatic enzyme lipase. It also prevents the hydrolysis of triglycerides. Hence the unabsorbed fat is passed through the body.(7) (12

Phentermine-topiramate is an extended-release drug combination with phentermine (which is a combination drug used for weight loss) and topiramate (a partial onset, primary generalized tonic-clonic seizure medicine, also prescribed as a prophylactic migraine drug). The FDA approved this drug combination in 2012.(13) It works by suppressing the appetite and increasing the metabolism. (14)

Tirzepatide is a synthetic form of glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), that works by activating receptors for these two hormones secreted from the intestine. The drug reduces the secretion of the glucagon hormone (involved in regulating appetite), and slows down gastric emptying. (5) (15) This eventually reduces appetite and calorie intake. Other GLP-1 agonists include Exenatide, Liraglutide, Dulaglutide, and Semaglutide. (15)

The GLP-1 agonists are prescribed for patients dealing with type 2 diabetes for the past fifteen years. This is because type 2 diabetes patients secrete less (GLP-1) and GLP-1 agonists provide just that, albeit synthetically. Hence, given the FDA’s approval, these diabetes medications for weight loss work just as fine, as shown in clinical trials.(5) (7) (16

Setmelanotide is used to treat genetic obesity by restoring appetite control. It acts on the melanocortin-4 receptor (MC4R) and acts against the mutations/deficiencies in the proopiomelanocortin (POMC), proprotein convertase subtilisin/kexin type 1 (PCSK1), or leptin receptor (LEPR) genes. These genetic variations/deficiencies otherwise lead to hyperphagia, and increased risk for metabolic co-morbidities along with childhood obesity. (17) (18)

Are Children And Teenagers Allowed To Take Weight Loss Medications?

The US FDA has approved orlistat, liraglutide, phentermine-topiramate, and semaglutide for children aged 12 years and above, and adults as prescription weight loss medication. For children aged 6 years and above, with genetic obesity, the FDA has recently approved Setmelanotide.(3)

Weight Loss Medication: Is It A Substitute For Healthy Eating And Exercise?

No weight loss medication is prescribed to replace a healthy diet and physical activity. Prescription weight loss pills are given only because one harbours a system which needs help in recovering from obesity. Even the best weight loss medication will take a person only so far in his/her/their weight loss journeys. Beyond a certain point, one must be driven about their own health and responsibilities.

Most weight loss drugs are prescribed for a period of twelve weeks to up to a year depending on the severity of obesity and the level of body weight reduction desired. After dosing is complete and a certain amount of body weight has been reduced, one needs to ensure a nutrition-rich diet, physical activity, and adequate sleep to fix the body’s digestion, metabolism, and absorption process. 

Even after taking weight loss pills, one must ensure 150 mins of moderate aerobic exercise and twice weekly strengthening and muscle building workouts to maintain their target weight. It is important to understand that there might be an initial increase in weight right after one stops taking weight loss pills, but if the physical activities and optimal nutrition are maintained, one can definitely control their weight loss journey. 

The Ultimate Goal For Weight Loss Management

A standard target for prescription weight loss pills is a 3-5% loss of body weight within the first twelve weeks of prescription. Further, a specialist can recommend a change in medication if there is no weight loss after the first twelve weeks of prescription. (3)

Some drugs are also prescribed for anytime between five months to a year to reach optimal dosage, for an overall reduction of 5-10% body weight to reduce risks of metabolic, skeletal, and anatomical complications due to obesity. However, further weight reduction (>15%) is targeted for cardiovascular disorders as per patient medical histories. (2) In extremely rare cases, a lifelong course of weight loss pills is prescribed, but only when specified by an examining nutritionist, endocrinologist, or bariatric surgeon. (19)

The Bottom Line Remains…

Dealing with obesity is a tricky affair indeed. The only markers of a metabolic disorder like obesity are comprehensive medical reports of blood, serum, and urine, along with analytical tests for cardiovascular functions, along with other tests prescribed by specialists.

If a person can manage his/her/their own body weight by improving on lifestyle, diet, and sleep patterns, it is always advisable. However, if these interventions are also failing to bring the body weight down (especially for people with a BMI of ≥27~30 kg/mor/and those suffering from hypertension or type 2 diabetes), one needs to consult a specialist physician who will prescribe weight loss medication to bring the body weight down by a certain percentage before resorting to further lifestyle interventions. 

However, it should ALWAYS be remembered that prescription weight loss medication does not absolve anyone from maintaining steady physical activity and a healthy, nutrition-rich diet. Patients suffering from diabetes and cardiovascular diseases will always have accessory, ongoing medication even after the weight loss treatments are done with.


Q. What are the side effects of weight loss medications?

Q. What are the side effects of weight loss medications?

A. The most common side-effects of weight loss medications include nausea, constipation, and diarrhoea. However most cases are mild and resolve with time. If any adverse effect persists, please contact your physician who recommended the medications.

Q. Can weight loss supplements cause any harm?

A. Severe side effects of weight loss supplements (those not regulated by the FDA and sold like weight loss meds online) include liver damage, kidney issues, rectal bleeding, diarrhoea, and sleeplessness, among others. Please keep an eye out for compounds like ephedra, hydroxycut, fenfluramine, rimonabant, and sibutramine which have been recalled and banned from the market due to their associations with severe health risks like jaundice, stroke, heart attack and lung damage.

Q. Which are the best prescription weight loss pills?

A. Every weight loss pill has its own mechanism of action and acts differently in different systems. It is impossible to suggest a single model that works for all. There have been clinical studies validating the significant contribution of Semaglutide wherein it caused ~11-15% weight loss for a group of patients. But the overall sample size was not enough for generalizing the drug as the best weight loss medication.

Q. Are diabetes medication for weight loss as effective?

A. GLP-1 agonists are the main class of diabetes medications which are also prescribed for weight loss programs. Recent clinical trials have also shown that Tirzepatide was effective in reducing 15-20% or more of the body weight within 68-72 weeks. However, this refers to prolonged treatment regimen for more than a year and can be only taken if prescribed by physicians or endocrinologists. Diabetes medications for weight loss are effective but any one medication cannot be generalised as the best diabetes drug for weight loss.

Q. What are the best weight loss pills for women?

A. In weight loss medication, there is no ‘one size fits all’ model. However, pregnant women are advised against consuming any weight loss medication unless specifically instructed by gynecologists or specialist physicians.



  • Franz MJ. Weight Management: Obesity to Diabetes. Diabetes Spectr Publ Am Diabetes Assoc. 2017 Aug;30(3):149–53.

  • Chakhtoura M, Haber R, Ghezzawi M, Rhayem C, Tcheroyan R, Mantzoros CS. Pharmacotherapy of obesity: an update on the available medications and drugs under investigation. eClinicalMedicine [Internet]. 2023 Apr 1 [cited 2023 Nov 28];58. Available from:

  • National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. [cited 2023 Nov 29]. Prescription Medications to Treat Overweight & Obesity - NIDDK. Available from:

  • Commissioner O of the. FDA. FDA; 2023 [cited 2023 Nov 28]. FDA Approves New Medication for Chronic Weight Management. Available from:

  • Yale Medicine [Internet]. [cited 2023 Nov 29]. Do Anti-Obesity Medications Really Work? Available from:

  • AGA Clinical Practice Guideline on Pharmacological Interventions for Adults With Obesity - Gastroenterology [Internet]. [cited 2023 Nov 29]. Available from:

  • Obesity Medicine Association [Internet]. [cited 2023 Nov 29]. Top Weight Loss Medications. Available from:

  • Office of Dietary Supplements - Dietary Supplements for Weight Loss [Internet]. [cited 2023 Nov 29]. Available from:

  • Office of Dietary Supplements - Dietary Supplements for Weight Loss [Internet]. [cited 2023 Nov 29]. Available from:

  • Ansari RM, Omar NS. Weight Loss Supplements: Boon or Bane? Malays J Med Sci MJMS. 2017 May;24(3):1–4.

  • Sherman MM, Ungureanu S, Rey JA. Naltrexone/Bupropion ER (Contrave). Pharm Ther. 2016 Mar;41(3):164–72.

  • Bansal AB, Al Khalili Y. Orlistat. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Nov 29]. Available from:

  • Johnson DB, Quick J. Topiramate and Phentermine. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Nov 29]. Available from:

  • Lonneman DJ, Rey JA, McKee BD. Phentermine/Topiramate Extended-Release Capsules (Qsymia) for Weight Loss. Pharm Ther. 2013 Aug;38(8):446–52.

  • Weight Loss Medications: Do They Work? [Internet]. [cited 2023 Nov 29]. Available from:

  • Wilding JPH, Batterham RL, Calanna S, Davies M, Van Gaal LF, Lingvay I, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021 Mar 18;384(11):989–1002.

  • Hussain A, Farzam K. Setmelanotide. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Nov 29]. Available from:

  • Trapp CM, Censani M. Setmelanotide: a promising advancement for pediatric patients with rare forms of genetic obesity. Curr Opin Endocrinol Diabetes Obes. 2023 Apr;30(2):136–40.

  • Tchang BG, Aras M, Kumar RB, Aronne LJ. Pharmacologic Treatment of Overweight and Obesity in Adults. In: Feingold KR, Anawalt B, Blackman MR, Boyce A, Chrousos G, Corpas E, et al., editors. Endotext [Internet]. South Dartmouth (MA):, Inc.; 2000 [cited 2023 Nov 29]. Available from:


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