The Hidden Factor That May Make Protein Less Effective For Muscle

You can eat plenty of protein and still feel like your muscle-building efforts aren't going anywhere.

Maybe you're lifting regularly, adding protein to your meals, and doing all the "right" things, yet your strength or muscle mass isn't changing much. Protein gives your muscles the building blocks they need, but your body also has to be able to use them.

Researchers analyzed data from PRIMe, short for Protein Recommendation to Increase Muscle.

This randomized pilot trial was designed to see whether increasing protein intake could help people with stage II-IV colorectal cancer maintain muscle during chemotherapy.

Participants received individualized nutrition counseling to aim for either 1.0 or 2.0 grams of protein per kilogram of body weight per day over 12 weeks.

For this follow-up analysis, researchers looked at 50 participants, who were 57 years old on average.

Participants increased their protein intake during the study, but their muscle response varied. One factor that stood out was IL-6, a protein involved in the body's inflammatory response.

How much additional protein participants ate mattered, too.

Those who increased their daily intake by at least 27 grams saw measurable improvements in lean soft tissue by six weeks. That's roughly the amount in a scoop of protein powder or a protein-rich snack.

Researchers also found that baseline IL-6, insulin, several amino acids, and changes in protein intake together explained 77% of the variation in lean soft tissue response at six weeks.

Think of protein as the raw material your muscles need to repair and build tissue.

Your body breaks protein down into amino acids, which then help stimulate muscle protein synthesis, the process of making new muscle proteins.

Inflammation may interfere with that process by making muscle less responsive to those signals. Researchers call this anabolic resistance, which essentially means muscle doesn't get the same building response from a given amount of protein.

That could help explain why two people can eat similar amounts of protein and see different results. Having enough protein available matters, but so does how well the body responds to it.

This research doesn't mean you should automatically eat more protein or try to lower your inflammation based on an IL-6 result.

Getting enough protein and doing resistance training remain important for maintaining and building muscle.

But if you're consistently struggling to build or maintain muscle despite eating enough protein and exercising, particularly if you have an underlying health condition, it's worth discussing with your doctor.

Sleep, regular movement, overall diet, and other aspects of your health can also influence how your body responds to nutrition and training.

For now, the more useful way to think about this research is that muscle health isn't just about hitting a protein target.

Your body also needs to be in a position to put that protein to work.

In people with colorectal cancer, higher IL-6 levels were linked to smaller muscle gains after increasing protein intake.