"You can lose weight faster than ever with these new drugs, but there's a big problem with them."

In recent times, weight-loss medications have become true star drugs, and new developments aim to address the issue of weight loss without muscle loss. Several pharmaceutical companies are working on a solution, particularly those that missed out in the first round of the obesity drug market, but even the market leader Novo Nordisk is not idle  - as revealed in a Bloomberg article.

Recently, more effective weight-loss drugs than ever before have hit the market after it was discovered that several already approved medications have this beneficial "side effect." The demand has grown so much that Novo Nordisk announced it cannot produce enough of its drug, and the company's stock has soared, making the Danish firm the largest by market capitalization in Europe. Seeing the market potential, many pharmaceutical companies have prioritized the development of weight-loss drugs, seeking solutions that allow patients to lose fat while preserving their muscle mass.

When rapid weight loss occurs, whether due to medication or surgery, there is a higher risk of unhealthy muscle loss, as the body turns to muscle tissue for energy during a caloric deficit to survive the starvation period. If patients stop taking the drugs and regain weight, they may put on more fat than muscle, ultimately negatively impacting their health. Bloomberg outlines this issue with current weight-loss drugs. However, maintaining a higher muscle mass can help patients avoid rapid weight regain after they stop taking the medications, as more muscle mass leads to a different metabolic rate.

For now, Novo Nordisk's Wegovy and Eli Lilly's Zepbound are the leading therapies in the weight-loss market, which Goldman Sachs estimates could grow to $100 billion by 2030. Morgan Stanley also predicts a market close to $80 billion.

The two leading companies are also investigating treatments that help patients retain muscle while losing weight, and they are not alone in this effort. This development line could be particularly interesting for those who missed out on the first generation of obesity treatments and are now trying to establish themselves in a rapidly growing and highly profitable market. Preserving muscle mass will play a crucial role in the next phase of development, according to the chief scientist at Amra Medical.

According to recently released experimental data from Regeneron Pharmaceuticals, their cocktail increased muscle mass in subjects during a small-scale trial. Meanwhile, Eli Lilly paid $2 billion last year for a startup with an experimental drug that promises fat reduction while maintaining muscle mass.

A protein is responsible for muscle mass reduction. In the 1990s, scientists discovered through research on mice that they could neutralize the gene causing its production. This approach has long been tried for treating muscle-wasting disorders, with limited success so far. Now, Regeneron is recruiting hundreds of volunteers to test its antibodies, which will be administered alongside Novo Nordisk's drug. They are currently seeking healthy patients and plan to include the first obese patients in the trials starting mid-year.

Eli Lilly has similar plans, aiming to study its weight-loss drug Zepbound in combination with a treatment that has shown promise in preventing muscle wasting in older adults. The company is already testing the drug bimagrumab—which it acquired last year through the purchase of the startup Versanis Bio—to see if it promotes weight loss while preserving muscle mass.

To accelerate progress, some companies are turning to drugs originally developed for other diseases. Swiss pharmaceutical company Roche sees potential in combining an experimental muscle-wasting drug with a weight-loss treatment, which it acquired through the $3 billion purchase of Carmot Therapeutics.

The development lead at Novo Nordisk also stated that they are already working on compounds to preserve muscle mass. However, he believes that the rate of muscle loss during weight loss achieved with Wegovy is not unhealthy.

He adds that there is already a proven way to retain more muscle during weight loss, and that is exercise.

During a study conducted in Denmark testing their older obesity drug, it was found that patients who exercised lost twice as much fat as those who only took medication. Those who took the medication without exercising didn't necessarily lose less weight, but they were more likely to lose muscle along with fat.

According to some doctors interviewed by Bloomberg, weight loss is more important for many obese patients, even if they lose muscle along with fat.