Eli Lilly and Co. (LLY  ) has come out on top in a weight loss drug competition in a recent study. The study found that patients on Lilly's Mounjaro lost more weight than those on Novo Nordisk's (NVO  ) Ozempic.

What Happened: The study, published on the JAMA Internal Medicine website, analyzed the electronic health records of approximately 41,000 obese or overweight patients who were prescribed these drugs.

It revealed that Mounjaro users experienced a mean loss in body weight of 5.9% at three months, compared to 3.6% for Ozempic users. At six months, the mean loss was 10.1% for Mounjaro users versus 5.8% for Ozempic users.

At 12 months, the mean body weight loss was 15.3% for Mounjaro users and 8.3% for Ozempic users. The risk of gastrointestinal adverse events was similar for both drugs.

Mounjaro's active ingredient is tirzepatide, while Ozempic's is semaglutide. Lilly markets tirzepatide for diabetes as Mounjaro and for weight loss as Zepbound. Similarly, Novo markets semaglutide for diabetes as Ozempic and for weight loss as Wegovy. Both tirzepatide and semaglutide belong to a class of drugs known as GLP-1s.

Why It Matters: The findings come amid increasing scrutiny and competition in the weight loss drug market. Novo Nordisk has faced criticism over the high prices of its medications, Ozempic and Wegovy. The company has disclosed that it retains about 60% of the list price in the U.S. after rebates and fees.

Additionally, a recent observational study has linked Novo Nordisk's GLP-1 drugs, Ozempic and Wegovy, to a serious eye condition called nonarteritic anterior ischemic optic neuropathy (NAION), which can cause vision loss. This condition, which involves a loss of blood flow to the optic nerve, was highlighted in a study.

Meanwhile, in response to the growing demand for GLP-1 drugs, Novo Nordisk announced a $4.1 billion investment to expand its U.S. manufacturing operations.

Price Action: Eli Lilly and Co. stock closed at $918.00, up 0.38% on Monday. In after-hours trading, the stock increased 0.30%. Year to date, Eli Lilly's stock has risen by 55.02%.

Meanwhile, Novo Nordisk closed at $143.07, up by 0.49% on the same day. Year to date, Novo Nordisk's stock has grown by $40.96, reflecting a 40.11% increase, according to data from Benzinga Pro.