A recent study from the University of Pennsylvania found that intermittent use of GLP-1 drugs could actually have the opposite effect of what users intend.
Researchers in Penn's Leong Lab studied mice over a four-month period, cycling them on and off semaglutide - the active ingredient in medications such as Ozempic.
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"We started with both groups on the Sema, take them off, put them back on, put them back on. We did that twice," said research specialist Anna Son. "What we saw was that this group was gaining weight, and what they gained was fat."
Scientists said the drug appeared to become less effective after interruption, even after the mice got back on for a second cycle and stayed on consistently for 62 days.
GLP-1 medications have surged in popularity, with roughly one in eight adults using them for weight loss. However, researchers note that consistency is a major hurdle, with more than half of users discontinuing the medication within two years, often restarting later.
"It's because the people we know who are on GLP-1 constantly discontinue and restart their medication," said Emmanuel Rapp a graduate student at Penn's Leong Lab. "It shows this drug develops some sort of therapeutic resistance that makes it not as effective anymore."
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Doctors say weight loss from GLP-1 medications typically includes a mix of 40 percent muscle and 60 percent fat. Doctors say those who start and stop the drug will likely encounter the same issue as the mice.
While the study was conducted in mice, researchers say the findings raise concerns about how intermittent use could impact human patients. More research is needed to determine whether similar effects occur with other weight-loss medications, including newer drugs such as those used in Zepbound.
Experts say the key takeaway is consistency.