Weight-loss medicines such as Ozempic and Wegovy have become very popular in recent years.
These drugs belong to a group called GLP-1 medications, which help people lose weight by reducing appetite and slowing how quickly food leaves the stomach.
Many people have found them helpful, especially when combined with healthy eating and exercise.
However, a new study from researchers at the University of Pennsylvania suggests that how these drugs are taken may be just as important as the drugs themselves. The study found that stopping and restarting GLP-1 medications may reduce how well they work over time.
The research was carried out at the Perelman School of Medicine and published in the Journal of Clinical Investigation Insight. It focused on what happens when people do not take these medications consistently. This is a common situation, as many people stop taking weight-loss drugs after a period of time and later start again.
To explore this, scientists studied overweight mice over four months. One group of mice received a GLP-1 drug called semaglutide continuously throughout the study. The other group followed a “stop-and-start” pattern. They took the drug for two weeks, then stopped for two weeks, repeating this cycle several times before finally switching to continuous use.
At the beginning, both groups lost a similar amount of weight. However, the differences became clear over time. The mice in the stop-and-start group regained weight during each break from the drug. More importantly, when they started the medication again, they were not able to lose as much weight as before.
Even after returning to regular use for the final part of the study, the stop-and-start group remained about 20 percent heavier than the group that had taken the drug continuously. This suggests that inconsistent use may lead to weaker results over time.
Researchers believe this effect may be linked to changes in body composition. When people lose weight using GLP-1 drugs, the weight loss includes both fat and muscle. On average, about 60 percent of the weight lost is fat, and about 40 percent is muscle.
When the medication is stopped and weight is regained, most of the weight that comes back is fat, not muscle. This changes the balance between muscle and fat in the body. By the time the medication is started again, the body may be less willing to lose more weight, possibly to protect muscle levels.
Scientists describe this as the body reaching a “muscle floor.” At this point, the body may resist further weight loss because it senses that losing more muscle could be harmful. This may explain why restarting the medication does not produce the same results as before.
The lead researcher, Dr. Thomas H. Leung, explained that these findings highlight the importance of consistency. People who start GLP-1 medications may need to think of them as a long-term treatment rather than a short-term solution.
This idea is not completely new. Other treatments, such as hair growth medicines, also work best when used consistently. Stopping and restarting can reduce their effectiveness over time.
The study also points to the importance of protecting muscle while using these medications. Experts suggest that exercise, especially strength training, and proper nutrition can help maintain muscle mass. This may improve results and reduce some of the negative effects seen with stop-and-start use.
It is important to note that this study was done in animals, so more research is needed to confirm whether the same effects happen in humans. However, the findings still provide useful guidance for doctors and patients.
In the future, researchers also plan to study newer medications, such as tirzepatide, to see if they show similar patterns.
Overall, this study sends a clear message. Weight-loss medications can be effective, but they work best when taken consistently. Anyone considering these drugs should speak with their doctor to understand the commitment involved and to develop a plan that supports long-term success.
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