An honest look at what GLP-1 medications have been shown to do, what the labels warn about, and the open questions that a licensed provider should talk through with you.
Any medication strong enough to change body weight by 15 to 20 percent on average is strong enough to deserve a careful look at the downside. GLP-1 medications have an unusually large evidence base for a new class of drug, which means both the benefits and the risks are better documented than the marketing on either side suggests. This article is an educational overview, not medical advice, and it cannot tell you whether the balance tips one way or the other in your case.
Meaningful weight reduction. In the pivotal trials, average weight change was -14.9 percent with semaglutide 2.4 mg over 68 weeks (STEP 1) and up to -20.9 percent with tirzepatide 15 mg over 72 weeks (SURMOUNT-1), compared with 2 to 3 percent in the placebo groups that received the same lifestyle counseling. These are averages; some people respond much more, some much less.
Cardiovascular risk reduction (semaglutide). The SELECT trial followed 17,604 adults with established cardiovascular disease and a BMI of 27 or higher but no diabetes. Semaglutide 2.4 mg reduced the composite of cardiovascular death, nonfatal heart attack and nonfatal stroke compared with placebo. This led to an FDA-approved indication for cardiovascular risk reduction in that population. Tirzepatide's equivalent outcomes trial was still underway at the time of writing.
Improvements in weight-related conditions. The SURMOUNT-1 investigators reported improvements across all prespecified cardiometabolic measures, including blood pressure, lipids and glucose. Tirzepatide is additionally approved for moderate to severe obstructive sleep apnea in adults with obesity, and semaglutide holds an accelerated approval for a form of fatty liver disease (noncirrhotic MASH with moderate to advanced fibrosis).
A biological lever, not just willpower. Perhaps the most underappreciated benefit is that these medications act on the appetite system itself. People who have struggled with hunger and food preoccupation for decades often describe the quieting of those signals as the real change. That is not a results claim; it is a description of the mechanism reflected in the trial data on food intake.
The prescribing information for both Wegovy and Zepbound carries a boxed warning and a list of warnings and precautions. In plain language:
The most frequently reported adverse reactions are gastrointestinal: nausea, diarrhea, vomiting, constipation and abdominal pain, followed by headache, fatigue, dyspepsia and dizziness. Nausea was reported by 44 percent of participants on semaglutide 2.4 mg and by 25 to 29 percent of participants on tirzepatide across doses in the respective labels, versus 8 to 16 percent on placebo. These symptoms usually appear during dose escalation and ease over weeks for most people. Our side effects article covers practical management.
Hair thinning and changes in skin sensation (dysesthesia) also appear in the semaglutide label at low single-digit percentages at the standard dose, rising at the newer higher dose. Treatment discontinuation due to adverse events was 4.3 to 7.1 percent across tirzepatide doses in SURMOUNT-1, versus 2.6 percent for placebo.
Weight regain after stopping. In the STEP 1 extension study, participants who stopped semaglutide regained about two-thirds of their lost weight within a year, and most cardiometabolic improvements drifted back toward baseline. The authors concluded that obesity behaves as a chronic condition requiring ongoing treatment. This is not a flaw unique to GLP-1 medications; it is how body weight regulation works. But it means the decision to start is really a decision about long-term management.
Loss of lean mass. Any substantial weight loss includes some loss of muscle and other lean tissue, not just fat. A 2024 JAMA viewpoint by researchers from the National Institutes of Health and Washington University noted that this is expected and that its clinical importance depends on the individual, particularly older adults and anyone already at risk of frailty. Protein intake and resistance training are the two levers people have, and both have dedicated articles in this guide.
Compounded product quality. Compounded semaglutide and tirzepatide are not FDA-approved. The FDA has reported hundreds of adverse event reports for compounded versions, has flagged dosing errors from patients measuring their own doses from vials, and has found products arriving warm or carrying false labels. Buying from a licensed US pharmacy through a prescribing provider reduces these risks; it does not eliminate the fact that the product is not FDA-reviewed.
Unknowns. The approved products have roughly a decade of real-world use in diabetes and several years in weight management. Very long-term data in people without diabetes, data in people with lower BMIs, and data on off-label low-dose use are limited or absent.
Clinical guidelines generally frame these medications as tools for people whose weight is affecting their health, used alongside nutrition, activity and ongoing monitoring. The benefit side of the ledger is largest for people with higher BMIs and existing weight-related conditions, where modest percentage changes translate into meaningful health effects. The risk side grows with certain histories (thyroid cancer, pancreatitis, gallbladder disease, eating disorders, pregnancy plans) and with any plan to self-manage dosing or source medication outside a licensed pharmacy.
Gastrointestinal effects are the most common: nausea, diarrhea, vomiting, constipation and abdominal pain, followed by headache, fatigue and dizziness. In the labels, nausea was reported by 44% of people on semaglutide 2.4 mg and 25 to 29% on tirzepatide, and these effects usually cluster during dose escalation.
The approved labels list a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 as a contraindication, and advise caution with a history of pancreatitis, severe gastroparesis, pregnancy or pregnancy plans, and upcoming surgery under anesthesia. A licensed provider reviews your full history.
In the STEP 1 extension, people who stopped semaglutide regained about two-thirds of the weight they had lost within a year, and most cardiometabolic improvements drifted back toward baseline.
Any substantial weight loss includes some loss of lean tissue. Its clinical importance depends on the person, especially older adults and anyone at risk of frailty. Adequate protein and resistance training are the two recognized countermeasures.
Only a licensed provider who knows your history can weigh these factors for you. Bring your full medication list, any family history of thyroid cancer, and your own goals to that conversation. This article is educational and does not determine eligibility for treatment.
Written by the NewDay Wellness editorial team from the sources above and checked against them before publication, and medically reviewed by Dr. Sean Arora and Dr. Shannon Arora of Arora Health & Aesthetics; see our editorial standards. This article is educational and does not diagnose conditions, establish eligibility for any medication, or replace care from a licensed provider. Compounded medications are not FDA-approved.
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