Does Weight Loss Cause Muscle Loss? How to Preserve Muscle

Losing weight is usually discussed in terms of kilograms, stones, pounds or BMI. Increasingly, however, researchers are asking another important question:

What type of weight are we losing?

When body weight falls, not all of that reduction necessarily comes from body fat. Some loss of lean tissue can occur during most forms of significant weight loss, particularly when calorie intake falls substantially.

That has made preserving muscle an increasingly important part of modern weight management.

New research announced on 23 September 2026 highlights just how seriously scientists are taking the issue.

What is the new WVE-007 study?

Wave Life Sciences has started a Phase 2a study investigating an experimental medicine called WVE-007 alongside tirzepatide in adults living with obesity and type 2 diabetes.

WVE-007 is very different from currently available weight-management medicines. It is an RNA-based treatment designed to reduce production of a protein called Activin E by targeting the INHBE gene.

Researchers hope this approach could encourage loss of body fat while protecting lean muscle.

Earlier Phase 1 research with WVE-007 alone found reductions in total and visceral body fat while lean mass was maintained following a single dose.

The new trial will now investigate what happens when WVE-007 is used alongside weekly tirzepatide.

Has WVE-007 been shown to preserve muscle with tirzepatide?

Not yet.

This is an important distinction.

The combination trial has only just started, so there are currently no human results showing that WVE-007 plus tirzepatide produces more weight loss or better muscle preservation than tirzepatide alone.

Wave has reported encouraging combination results in preclinical animal studies, but animal findings cannot be assumed to produce the same results in people.

WVE-007 is also an investigational medicine and is not currently an approved weight-management treatment in the UK.

Do weight-loss medicines make you lose muscle?

Significant weight loss, whether achieved through dietary change, medication or surgery can involve loss of some lean mass as well as fat.

This does not automatically mean that someone is developing harmful muscle wasting.

Changes in body composition need to be interpreted alongside strength, physical function, protein intake, rate of weight loss, age and overall health.

The goal of good weight management should therefore be more than simply making the number on the scales fall.

How can muscle be protected during weight loss?

For most people, the fundamentals remain much less exotic than experimental RNA therapy.

Adequate protein intake, appropriate resistance or strength exercise, good overall nutrition and avoiding unnecessarily severe calorie restriction are important considerations.

A new JAMA commentary published on 23 September also argued that nutritional support should begin early in incretin-based treatment rather than waiting until appetite and food intake have already fallen substantially.

This is particularly relevant for people who find their appetite dramatically reduced and consequently struggle to eat enough protein or nutritionally balanced meals.

What about maintenance?

Muscle becomes particularly important when patients move from active weight loss into weight maintenance.

The aim at that stage is not necessarily to continue losing weight indefinitely. Maintaining strength, adequate nutrition, physical activity and a stable healthy weight may become more important than further reductions on the scales.

Future medicines may eventually allow clinicians to target body composition more precisely, but WVE-007 is still at an early experimental stage.

How Pharmulous can help

At Pharmulous, weight management is about more than achieving the lowest possible number on the scales.

Our clinical approach considers weight trajectory, nutrition, treatment response, side effects, lifestyle, muscle preservation and long-term maintenance.

Patients approaching their target weight can also be reviewed to discuss an appropriate maintenance strategy rather than assuming treatment should simply stop once a particular BMI or goal weight is reached.

New treatments such as WVE-007 are scientifically interesting, but current treatment decisions should continue to be based on licensed options, individual clinical assessment and established evidence.