Berkeley Scientists Find New Weight Loss Drug Without Muscle Loss

Millions of people struggling with obesity and diabetes may soon have a new treatment option that avoids the muscle loss and nausea common with current medications.

Scientists at UC Berkeley have discovered that a compound called TOFA helps the body burn fat by ramping up metabolism rather than cutting appetite. In mice studies published in Science Advances, the treatment led to weight loss from fat while preserving lean muscle mass.

The breakthrough comes as GLP-1 drugs like Ozempic and Wegovy have transformed metabolic disease treatment but created new challenges. While highly effective for weight loss, these medications can cause severe nausea and muscle loss that leads to frailty, especially concerning for long-term use.

"Body weight responds to two levers: taking in fewer calories, or spending more energy," said Anders Näär, professor of metabolic biology at UC Berkeley. "GLP-1s work almost entirely on the first, so we went after the second."

TOFA works through a dual mechanism that sets it apart from previously tested compounds. It blocks the production of fats like cholesterol and triglycerides while simultaneously activating genes that help cells burn fat for energy. In experiments, mice burned up to 18% more energy with no change in activity levels or body temperature.

The compound also improved insulin sensitivity, blood sugar control, and fatty liver disease in the test animals. Unlike similar drugs tested in the past, TOFA didn't raise triglycerides, a risk factor that has prevented other metabolism-boosting compounds from reaching approval.

Researchers found even more promising results when combining TOFA with existing GLP-1 medications. The combination produced greater improvements in weight, blood sugar, insulin levels, and triglycerides than either treatment alone, suggesting the approaches complement rather than compete with each other.

The Ripple Effect

This dual-action approach could reshape how doctors treat metabolic diseases affecting hundreds of millions worldwide. Preserving muscle mass matters enormously for aging populations, where maintaining strength prevents falls, enables independence, and extends healthy years of life.

The research team has already taken steps toward bringing TOFA to patients by founding ReRx Therapeutics with support from Berkeley's entrepreneurship programs. While human trials haven't begun, the strong safety profile and effectiveness in animal studies offer hope for a new class of metabolic treatments.

The discovery reminds us that scientific breakthroughs often come from asking different questions rather than just improving existing answers.