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How Do Ozempic, Wegovy, and Mounjaro Work? What to Know About Drugs Promising Weight Loss.

DISCLAIMER: The Kelly's Choice team are not medical doctors nor prescribing medications for weight loss. Our goal is to reach people where they are currently at on their health journey. This article is for educational purposes only.

There has been a recent uproar over the use of different medications by celebrities and influencers across the country that are promising weight loss. Some popular ones include Ozempic, Wegovy, and Mounjaro. Because of their rise in popularity, individuals who need these drugs are experiencing trouble receiving them. What exactly are these drugs and how do they work?

The Semaglutides: Ozempic and Wegovy - Mechanism of Action and Side Effects

Ozempic and Wegovy are considered semaglutides. These medications carry similar functions to the glucagon-like peptide-1 (also known as GLP-1) hormone that is in the body (Ghusn W, De la Rosa A, Sacoto D, et al). GLP-1 works to lower blood glucose by producing more insulin, which is why semaglutides are effective treatments for those with type 2 diabetes (Ghusn W, De la Rosa A, Sacoto D, et al). Higher amounts of GLP-1 (such as introducing a semaglutide injection) will affect the brain by inhibiting signals that affect appetite, which will help someone feel full faster and stay full for longer (Baggio, Laurie L, and Daniel J Drucker). Semaglutide, along with liraglutide, naltrexone in partnership with bupropion, orlistat, and phentermine with topiramate are the only drugs approved by the Food and Drug Administration (FDA) for weight loss (Ghusn W, De la Rosa A, Sacoto D, et al). Those individuals who qualify to use weight loss medications are individuals with a body mass index, BMI, of 30.0 or greater with no weight-related comorbidities or a BMI of 27.0 with weight-related comorbidities, including hypertension (high blood pressure), high LDL-cholesterol, low HDL cholesterol, or high levels of triglycerides, type 2 diabetes, and coronary heart disease (Ghusn W, De la Rosa A, Sacoto D, et al). Ozempic and Wegovy are administered as a weekly injection. The table below breaks down the side effects of Ozempic and Wegovy, which are often considered when deciding which one is best for the individual.

Side Effects when taking Ozempic (“Common Side Effects”):

  • Nausea

  • Stomach pain

  • Constipation

  • Diarrhea

  • Vomiting

Side Effects when taking Wegovy (“Common Side Effects of Wegovy”)

  • Nausea

  • Stomach pain

  • Dizziness

  • Stomach flu

  • Diarrhea

  • Constipation

  • Headache

  • Feeling bloated

  • Heartburn

  • Vomiting

  • Tiredness/fatigue

  • Belching

  • Runny nose or sore throat

  • Upset stomach/Gas

Another topic that is emerging in the media is “Ozempic face”. This is essentially fat loss in the face, which can lead to loosened skin around the eyes and the hallowing of cheeks. This makes the person taking Ozempic appear older because they lose subcutaneous fat in the face and their skin appears aged.

Tirzapatide: A New Class of Weight Loss Medication - Mechanism of Action and Side Effects

Mounjaro is another drug that is claimed to cause weight loss. Mounjaro is considered Tirzepatide and is also an anti-diabetic medication, which is the first in its class (“Welcome to Mounjaro”). Mounjaro works by targeting GIP and GLP-1, which increases insulin production when blood sugars are rising (“Welcome to Mounjaro”). Mounjaro also decreases food intake and slows gastric emptying (“Welcome to Mounjaro”). It does this by triggering hormones to improve glycemic control, making someone feel fuller longer (“Welcome to Mounjaro”). The table demonstrates the symptoms of Mounjaro.

Common side effects of Mounjaro (“Welcome to Mounjaro”)

  • Nausea

  • Diarrhea

  • Decreased appetite

  • Vomiting

  • Constipation

  • Indigestion

  • Stomach pain

Recent Research

The Semaglutide Treatment Effect in People with Obesity (STEP) trials published their results in 2022 and show the effectiveness of semaglutide for the treatment of obesity. This study reported that patients receiving 2.4 milligrams lost a mean of 6% of their weight by week 12 and 12% of their weight by week 28 (Ghusn W, De la Rosa A, Sacoto D, et al).

Although not indicated for weight loss, a clinical trial was just started that will compare the efficacy and safety of Tirzepatide (Mounjaro) compared to semaglutide 2.4 milligrams in adult participants who have obesity without any weight comorbidities or are overweight with weight-related comorbidities without diabetes (“A Study of Tirzepatide (LY3298176) in Participants With Obesity or Overweight With Weight Related Comorbidities (SURMOUNT-5)”). This study is expected to last around 78 weeks long and is estimated to have 700 participants. Given that this medication is one of a kind and is relatively new, there are limited studies that provide specific information, but many reports have shown the success of Mounjaro for losing and maintaining weight loss (Jastreboff et al).


Given this information, these drugs started as antidiabetic medication; however, over the years, they have shown promise and safety in losing and maintaining weight loss. These medications are most effective when paired with diet and lifestyle changes. It is important to discuss with your primary care provider if you are eligible for weight loss medication.


1. “A Study of Tirzepatide (LY3298176) in Participants With Obesity or Overweight With Weight Related Comorbidities (SURMOUNT-5)”. National Institute of Health U.S. National Library of Medicine. Updated May 6, 2023.

2. Baggio, Laurie L, and Daniel J Drucker. “Glucagon-like peptide-1 receptors in the brain: controlling food intake and body weight.” The Journal of clinical investigation vol. 124,10 (2014): 4223-6. doi:10.1172/JCI78371

3. “Common side effects”. Ozempic semaglutide injection. Updated June 2022.

4. “Common Side Effects of Wegovy”. Wegovy semaglutide injection. Updated May 2023.

5. Ghusn W, De la Rosa A, Sacoto D, et al. “Weight Loss Outcomes Associated With Semaglutide Treatment for Patients With Overweight or Obesity.” JAMA Netw Open. Vol. 5(9):e2231982. doi:10.1001/jamanetworkopen.2022.31982

6. Jastreboff et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 21 July 2022.

7. “Welcome to Mounjaro”. Mounjaro (tirzepatide) injection. Updated February 2023.


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