For anyone who's been following the meteoric rise of weight-loss injections like Ozempic and Wegovy, one thing is certain: these medications are effective but not for everyone. Now, a new, in-depth study might know why.Appearing in the journal Diabetes, Obesity and Metabolism, this new research has identified key determinants of who is most likely to thrive on GLP-1 receptor agonists (GLP-1RAs), a drug class that includes semaglutide (Ozempic/Wegovy). Ranging from use duration to body composition, and from metabolic rate to diabetic status, the results yield a finer set of directions for individualized obesity treatment—and may potentially minimize the guesswork that too often vexes patients and clinicians alike.GLP-1RAs are drugs initially made to treat type 2 diabetes but have produced miraculous outcomes for the treatment of obesity. They function by duplicating a hormone that occurs naturally in the body, which suppresses hunger and controls the blood sugar levels. Semaglutide, the drug behind Ozempic and Wegovy, has assisted individuals in losing an average of 15–21% of their body weight when combined with diet and lifestyle modifications.Even with all the news-grabbing changes and social media hype, results are all over the place. Some patients lose weight rapidly, others plateau, and some develop side effects such as nausea that cause them to quit cold turkey. The new research, performed at Peking University People's Hospital, sheds some light on why.Scientists monitored 679 overweight or obese patients who initiated GLP-1RA treatment between November 2022 and October 2024 at an obesity clinic in Beijing. For 12 months, they monitored a range of physical and metabolic factors to determine what characteristics were associated with improved outcomes.Patients taking GLP-1RAs for extended periods, particularly semaglutide, had higher odds of significant weight loss. But more than how long the patient was on the drug, study authors determined that individual traits mattered substantially in effectiveness.In particular, individuals who did not have diabetes, had a higher percentage of body fat, larger amounts of skeletal muscle, and a higher rate of basal metabolism were found to be more likely to succeed. Also, higher serum creatinine levels (a marker for muscle mass and kidney function) were associated with improved success.Role of Muscle Mass and MetabolismGLP-1s are effective devices, but they need to be combined with muscle-sparing measures. Most patients inadvertently lose lean muscle mass, which can lower metabolism and undermine long-term weight control.That is, the scale may fall, but what you lose is important. Retaining muscle mass is essential to long-term health and success. Because of this, experts suggest a two-prong approach: savvy, high-protein eating and regular strength training to help maintain lean tissue throughout treatment.5 Body Traits That Predict If You'll Actually Lose Weight on GLP-1 DrugsNew research is showing that not everyone responds the same way to GLP-1 receptor agonists—and your body’s makeup may be the key to understanding why. Here are five physical traits that strongly predict whether you’ll shed pounds successfully while on these weight-loss medications:1. Higher Body Fat PercentageIndividuals with excess body fat at the beginning of treatment respond to GLP-1 drugs more favorably. Why? They attack hunger and fat storage, so people with more to lose are more likely to see faster and more dramatic results.2. Increased Skeletal Muscle MassMuscle is not only for power—it burns calories even at rest. Individuals with greater skeletal muscle mass (particularly in the arms, legs, and abdomen) tend to have a quicker metabolism, which can strengthen the actions of weight-loss drugs.3. Increased Basal Metabolic Rate (BMR)A greater BMR indicates that your body expends more energy on a daily basis. Individuals with naturally quicker metabolisms are more apt to experience efficient and long-lasting weight loss when taking GLP-1RAs such as semaglutide.4. Greater Serum Creatinine LevelsThis marker is most commonly associated with muscle mass and kidney function. Individuals with slightly elevated (but normal) levels of creatinine—usually an indicator of greater lean body mass—tended to respond more favorably to these drugs.5. No Diagnosis of DiabetesAgainst expectation, individuals with no diabetes experienced more success than those with diabetes. This could be explained by improved insulin sensitivity, reduced metabolic resistance, or fewer pre-existing complications that would interfere with weight reduction.How Your Diabetes Status Is Important?The research demonstrated that those without diabetes had considerably higher chances of being successful with weight loss compared to those with prediabetes or diabetes. This could be because of deep-rooted metabolic distinctions or that GLP-1RAs react differently in states of insulin resistance.Lead researcher Dr. Linong Ji described, "This study highlights the value of metabolic state-matched strategies. Individuals with diabetes can benefit from a different or more combined regimen." Consistency is key, patients who remained on the drug for a longer period were more likely to lose weight. Those who dropped out early because of side effects, lack of response, or lifestyle interference were far less successful.This accords with demands from doctors for improved support for adherence. Greater follow-up frequencies, tailored coaching, and symptom control can avert early dropouts."Adherence to medication is neglected but equally important as the medicine itself," the authors stated. "Physicians must assist patients in staying on track, especially for the first months or so."Side Effects of GLP-1 DrugsSide effects, particularly gastrointestinal such as nausea, constipation, or vomiting, are still the number one reasons individuals drop out of GLP-1RAs. That's where tailoring treatment comes into play even more so.Take, for instance, individuals who have less skeletal muscle mass. These individuals are likely to be more susceptible to fatigue and muscle wasting, enhancing dropout risk. Tweaking dose schedules, incorporating physical therapy, or emphasizing diet quality can all help mitigate these problems.The global rise of drugs like Wegovy isn’t just hype. These medications are proving to be some of the most effective tools we’ve ever had in the fight against obesity, a condition affecting over 650 million people worldwide but what this new study makes clear is that weight loss is not one-size-fits-all, even with powerful drugs. Body composition, muscle mass, metabolic health, and individual biology all play a role.For doctors, that equates to taking a precision medicine approach—tailoring treatments based on an individual's profile, instead of simply dosing all patients the same.And for patients? It's a reminder that medications such as Ozempic and Wegovy can be remarkably powerful but only as part of an integrated, personalized plan that values the complexity of your body.GLP-1 medications are revolutionizing weight control, but as this study reveals, success is not arbitrary success is individual. Understanding what influences results can enable more individuals to achieve potential through progress.