Semaglutide is a medication that is used to treat type 2 diabetes (trade name Ozempic).  Not only does it improve blood sugars more than any other medication that it has been compared to (so far) in the diabetes world, but it is also very effective to help with weight loss.  Thus, semaglutide is currently under study as a medication to treat obesity in people without diabetes.

We have now completed the first study of semaglutide as an obesity treatment.  The study, published in The Lancet, in which I was an investigator and also an author of this paper, randomized 957 people to receive various doses of once daily semaglutide, with liraglutide 3mg and placebo as controls. (Liraglutide 3mg is also called Saxenda, which is a medication already in use for treatment of obesity.)

At 1 year, 93% of patients were retained in the trial, which is much better than most studies of weight loss medication, which tend to have much less follow up data. Overall, 81% of patients completed the full year of treatment. A higher percent of the placebo group (24%) stopped treatment than did those on semaglutide (18%).

The weight loss after one year on semaglutide was impressive, ranging from -6.0% weight loss on the lowest tested dose of semaglutide (0.05mg per day) to an impressive -13.8% weight loss on the highest dose tested (0.4mg per day), compared to -2.3% weight loss on placebo and -7.8% on liraglutide 3mg per day.

The weight loss had not plateaued by one year on the highest doses of semaglutide, suggesting that if the study had been longer than a year, even more weight loss may have been seen.

In terms of side effects, gastrointestinal were most common (e.g. nausea), in keeping with what we already know about this class of medication; these side effects increased with higher doses of semaglutide, and were a little higher on the highest semaglutide dose than on liraglutide 3mg.  There was also a higher risk of gallbladder side effects (e.g. gallstones), which was a little more common on the highest dose of semaglutide compared to placebo.

The weight loss seen in this study is more than has been seen with any other existing weight loss medication.  The next phase of studies of semaglutide for weight loss is underway.

Disclaimer: I was a principal investigator in this research trial and an author of the paper discussed. I am/have been involved in other trials of semaglutide and liraglutide as an obesity treatment.  I receive honoraria as a continuing medical education speaker and consultant from the makers of semaglutide and liraglutide (Novo Nordisk). 

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