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, Dr. Stanford told this news organization. “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,” Dr. 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, Dr. 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 Dr. 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.”