New weight loss drugs preserve muscle and cut fat

Muscles do more than provide strength; they help regulate metabolism. During weight loss the body usually sheds both fat and some muscle, and faster weight loss often means greater muscle loss. That has emerged as a problem with GLP-1 treatments such as Ozempic, Mounjaro, and Zepbound, where some patients lose substantial muscle and become frail.

A new generation of therapies aims to protect lean mass while reducing fat. Examples include bimagrumab (acquired by Eli Lilly for $1.9 billion), SPX-001 (purchased by AstraZeneca for about $300 million in 2025), and Novo Nordisk’s CagriSema. Cambrian Biotech’s ATX-304 is an oral “exercise mimetic” the company says increases metabolic rate; in a 23-person safety trial it raised resting metabolism and trimmed roughly 5% of visceral fat, with a midsize trial due to read out at the end of 2027.

Many of these efforts recycle drugs that failed for other purposes.

weight loss, muscle loss, glp-1, ozempic, mounjaro, zepbound, bimagrumab, cagrisema, atx-304, visceral fat