Why Do GLP-1 Drugs Stop Working, and What to Do About It?

 There's no question that glucagon-like peptide 1 (GLP-1) agonists represent a major advance in the treatment of obesity for patients with or without diabetes. In clinical trials, participants lost 15%-20% of their body weight, depending on the drug.

But studies also have shown that once people stop taking these drugs — either by choice, because of shortage, or lack of access — they regain most, if not all, the weight they lost.

Arguably more frustrating is the fact that those who continue on the drug eventually reach a plateau, at which point, the body seemingly stubbornly refuses to lose more weight. Essentially, it stabilizes at its set point, said Fatima Cody Stanford, MD, MPH, MPA, MBA, an obesity medicine physician at Massachusetts General Hospital and associate professor at Harvard Medical School in Boston.

'Tug of War'

Every study of weight loss drugs done over the past 40 years or so shows a plateau, Stanford told Medscape Medical News. "If you look at the phentermine/topiramate studies, there's a plateau. If you look at the bupropion/naltrexone studies, there's a plateau. Or if we look at bariatric surgery, there's a plateau. And it's the same for the newer GLP-1 drugs."

The reason? "It really depends on where the body gets to," Stanford said. "The body knows what it needs to do to maintain itself, and the brain knows where it's supposed to be. And when you lose weight and reach what you feel is a lower set point, the body resists."

When the body goes below its set point, the hunger hormone ghrelin, which is housed in the brain, gets reactivated and gradually starts to reemerge, she explained. GLP-1, which is housed in the distal portion of the small intestine and in the colon, also starts to reemerge over time.

"It becomes kind of a tug of war" between the body and whatever weight loss strategy is being implemented, from drugs to surgery to lifestyle changes, Stanford said. "The patient will start to notice changes in how their body is responding. Usually, they'll say they don't feel like the treatment is working the same. But the treatment is working the same as it's always been working — except their body is now acclimated to it."

Anne L. Peters, MD, CDE, professor and clinical scholar, Keck School of Medicine of the University of Southern California, and director, agreed that in the simplest terms, a plateau occurs because "the body becomes more and more used to" the weight loss intervention.

However, when you lose weight, you lose both fat mass and lean body mass, and lean body mass is the metabolically active part of your body, explained Peters. "That's what burns and basically makes up your basal metabolic rate."

With weight loss, the metabolism slows down, she said. If patients need 2000 calories a day to survive at a certain weight and then lose 50 pounds, they may then need only a 1000 calories a day. "With any obesity treatment, you reach a point at which your metabolic rate and your daily caloric requirements become equal, and you stop losing weight, even though your daily caloric requirement is less than it was when your weight was higher."

Managing the Plateau

Several strategies can be used to help patients break through a plateau. One is to try multiple weight loss agents with different targets — something often done in the real world, Stanford said. "You don't see this in the studies, which are focused on just one drug, but many of our patients are on combination therapy. They're on a GLP-1 drug plus phentermine/topiramate plus metformin, and more. They're usually on three, four, five drugs, similar to what we would see with resistant hypertension."

If a patient plateaus on a GLP-1 drug, Stanford might add phentermine. When the patient reaches a plateau on phentermine, she would switch again to another agent. "The goal is to use agents that treat different receptors in the brain," she said. "You would never use two GLP-1 agonists; you would use the GLP-1, and then something that treats norepinephrine, for example."

At the same time, Peters noted, "try to get them off the drugs that cause weight gain, like insulin and sulfonylurea agents."

Tapering the GLP-1 dose can also help, Peters said. However, she added, "If I'm using a GLP-1 drug for type 2 diabetes, it's different than if I'm using it just for weight loss. With type 2 diabetes, if you taper too much, the blood sugar and weight will go back up, so you need to reach a balance."

Peters has successfully tapered patients from a 2-mg dose down to 1 mg. She has also changed the strategy for some — ie, the patient takes the drug every other week instead of every week. "I even have a patient or two who just take it once a month and that seems to be enough," she said. "You want to help them be at the dose that maintains their weight and keeps them healthy with the least possible medication."

Emphasizing lifestyle changes is also important, she said. Although resistance training won't necessarily help with weight loss, "it's critical to maintaining lean body mass. If people keep losing and regaining weight, they're going to lose more and more lean body mass and gain the weight back primarily as fat mass. So, their exercise should include about half aerobic activity and half resistance training."

Long-term Journey

Setting appropriate expectations is a key part of helping patients accept and deal with a plateau. "This is long-term, lifelong journey," Stanford said. "We need to think about obesity as a complex, multifactorial chronic disease, like we think about hypertension or type 2 diabetes or hyperlipidemia."

Furthermore, and in keeping with that perspective, emerging evidence is demonstrating that GLP-1 drugs also have important nonglycemic benefits that can be achieved and maintained, Peters said. "Obviously weight loss matters, and weight loss is good for you if you're overweight or obese. But now we know that GLP-1 drugs have wonderful benefits for the heart as well as renal function." These are reasons to continue the drugs even in the face of a plateau.

One of Peters' patients, a physician with type 2 diabetes, had "fought with her weight her whole life. She's been on one or another GLP-1 drug for more than 15 years, and while none seem to impact her weight, she's gone from having relatively poorly controlled to now beautifully controlled diabetes," Peters said. "Even if she hasn't lost, she's maintained her weight, a benefit since people tend to gain weight as they get older, and she hasn't gained."

Another patient was disabled, on oxygen, and had recurrent pulmonary embolisms. "She weighed 420 pounds, and I put her on semaglutide because she was too sick to be considered for bariatric surgery." When that didn't work, Peters switched her to tirzepatide, gradually increasing the dose; the patient lost 80 pounds, her emboli are gone, she can walk down the street, and went back to work.

"Part of why she could do that is that she started exercising," Peters noted. "She felt so much better from the drug-related weight loss that she began to do things that help enhance weight loss. She became happier because she was no longer homebound."

This points to another element that can help patients break through a plateau over time, Peters said — namely, behavioral health. "The more people lose weight, the more they feel better about themselves, and that may mean that they take better care of themselves. The psychological part of this journey is as important as anything else. Not everyone has the same response to these agents, and there are all sorts of issues behind why people are overweight that physicians can't ignore."

"So, in addition to managing the drugs and lifestyle, it's important to make sure that people access the behavioral health help they need, and that once they break through a plateau, they don't develop an eating disorder or go to the opposite extreme and become too thin, which has happened with some of my patients," she said. "We need to remember that we're not just giving patients a miraculous weight loss. We're helping them to be healthier, mentally as well as physically."

Stanford disclosed that she had been a consultant for Calibrate, GoodRx, Pfizer, Eli Lilly, Boehringer Ingelheim, Gelesis, Vida Health, Life Force, Ilant Health, Melli Cell, and Novo Nordisk. Peters disclosed that she had been a consultant for Vertex, Medscape Medical News, and Lilly; received funding from Abbott and Insulet; and had stock options in Omada Health.

https://www.medscape.com/viewarticle/why-do-glp-1-drugs-stop-working-and-what-do-about-it-2024a10000ti