One of the reasons that medications known as GLP-1 agonists or dual agonists have been so effective for weight loss is because they counteract the body’s natural responses to increase hunger and promote weight gain. “These drugs mimic naturally occurring gut hormones that control hunger and give them back to individuals in fairly high amounts,” Kushner says. As a result, someone taking one of these medications doesn’t feel hungry, so they’re less likely to overeat.
It’s also been noted that these kinds of drugs dial back what is known as “food noise”: cravings, thoughts, and desires for food that can feel constant and intrusive. “Hunger is mediated by lots of things. Along with being habitual, it can be spiritual or emotional,” Youdim says. “When my patients take these drugs, they tell me they’re able to make sustained changes more effectively without all of this noise that gets in the way.”
Each drug uses a different active ingredient to accomplish these tasks. Wegovy and Ozempic contain semaglutide, and Mounjaro and Zepbound have tirzepatide. Another drug, Saxenda, contains liraglutide. The medications all work on receptors for GLP-1, mimicking the effects of that hormone when it comes to appetite and making you feel more full. In biochemistry, anything that causes a response in this way is called an agonist. Drugs that contain tirzepatide are known as dual agonists because they affect receptors for both GLP-1 and GIP.
In addition to helping you feel fuller, GLP-1 agonists slow the rate at which food empties from your stomach, which delays the usual hormonal signals to your brain indicating that you need to eat, says Daniel J. Drucker, MD, a senior scientist at Lunenfeld Tanenbaum Research Institute at Mount Sinai Hospital in Toronto. This twofold effect means you aren’t as hungry in general and may be able to go longer between meals without getting hungry.
People with obesity who took a GLP-1 agonist like semaglutide lost an average of about 15 percent of their total body weight, according to a study published in The New England Journal of Medicine. Dual agonists like tirzepatide may be even more effective, with an average weight loss of about 21 percent, according to results of a more recent study published in the same journal. “GIP most likely affects the same pathways in the brain as GLP-1 and gives you a little bit more of a boost in terms of satiety,” Wojeck says.
Of course, these medications aren’t for everybody. The U.S. Food & Drug Administration (FDA) approved these medications for people with a body mass index (BMI) of 30 or above, which is classified as obese, or anyone with a BMI of at least 27 and least one weight-related health issue like diabetes, high blood pressure, or cardiovascular disease. “These drugs are designed to treat medical issues, not cosmetic ones,” Youdim says.
As with any medication, GLP-1 agonists come with potential side effects. Researchers who analyzed more than 21,000 reports from the FDA’s adverse event database concluded that taking medications that contain semaglutide was significantly associated with an increased risk of gastrointestinal effects, including nausea, diarrhea, vomiting, constipation, and pancreatitis, according to results published in Frontiers in Endocrinology. There have also been reports, although infrequent (265 since 2010), of suicidal thoughts or behavior in people taking these or similar medications, according to Reuters. While additional research is needed, anyone who experiences these effects should consult their healthcare provider immediately.
While these new medications have shown enormous potential for treating obesity, experts stress that they are not a cure. They are most effective when used in conjunction with healthy lifestyle habits such as regular exercise, stress management, and a healthy diet, and they have to be taken long term, usually for life.
“The majority of people will gain back weight if they stop these medications,” Drucker says. “Obesity is a chronic health challenge, and just as you wouldn’t stop taking a blood pressure medication because you’ve reached a desired blood pressure, the same is true with treating obesity with these medications.” In fact, one study found that a year after individuals stopped taking semaglutide, they had regained two-thirds of the weight they had lost.
Traditional treatments for obesity have usually focused on lifestyle changes like diet and exercise, but new kinds of medications have revealed that human physiology is just as important a consideration. Hormones that control appetite, the satisfaction we get from food, and how our bodies use the calories we eat play a complex role in maintaining body weight, and researchers are learning more about them every day.
As research continues to advance, hopefully so may the treatment options for anyone struggling with weight. “When we learned how to treat high blood pressure and diabetes, a whole range of medications was developed, and I see the same happening for obesity, especially since we now have a target for helping people lose weight, namely these gut hormones,” Kushner says. ”These drugs are just the beginning.”
Everyday Health‘s Weight Loss Reframed Survey queried 3,144 Americans nationwide ages 18 and older who had tried losing weight in the previous six months. The study was fielded between July 10 and August 18, 2023, across demographic groups, genders, and health conditions. Survey recruitment took place via an online portal, in app, and via email. The margin of error for the sample size of 3,144 is +/-1.7 percent at a 95 percent confidence level.