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Protein Timing Doesn't Matter for Muscle Growth in Older Adults, New Trial Finds

Updated: August 5, 2026

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For years, gym advice has insisted that when you eat protein matters almost as much as how much you eat — especially a dose right after training or right before bed to feed muscles overnight. A new 12-week randomized controlled trial in older men puts that idea to a real test, and the results are clear: timing added nothing once total daily protein was already adequate.

How the study was designed

Researchers recruited 30 untrained older men (mean age 65.7 ± 4.0 years) and had them complete a supervised resistance training program twice a week for 12 weeks. Participants were randomly assigned to one of three groups:

Post-exercise protein (n=9): 40g of whey/casein immediately after each training session.
Pre-sleep protein (n=11): 40g of whey/casein 30 minutes before sleep.
Training-only (n=10): resistance exercise with no additional supplement.

Crucially, all participants already consumed at least 1.0 g of protein per kilogram of body weight per day from their regular diet before the study began — a detail that turns out to matter a great deal.

What the muscle and strength data showed

Over the 12 weeks, everyone got measurably bigger and stronger. Muscle thickness increased across the board:

Vastus lateralis: +0.16cm (95% CI 0.06–0.25)
Rectus femoris: +0.13cm (95% CI 0.03–0.23)
Vastus intermedius: +0.18cm (95% CI 0.05–0.31)

Strength gains were substantial too, with 1-repetition maximum (1-RM) improving by an average of +10.9kg (95% CI 5.50–16.3) on the chest press and +28.3kg (95% CI 19.63–37.1) on the leg press.

The catch: none of these gains differed significantly between the post-exercise, pre-sleep, or training-only groups. Adding 40g of protein at a specific moment around the workout or before bed simply didn't move the needle beyond what resistance training alone achieved.

Why timing took a back seat

The likely explanation is that these men were already meeting their daily protein needs before the study started. Once a baseline intake of roughly 1.0 g/kg/day or more is in place, the body appears to have enough amino acids circulating to support muscle repair and growth regardless of exactly when an extra dose arrives. In other words, the "anabolic window" — the idea that protein must land within a tight timeframe around exercise to be useful — looks far less important than simply hitting an adequate total for the day.

Practical takeaway

For older adults doing resistance training, this trial reinforces a simpler and more forgiving message:

Focus on total daily protein intake, not the exact minute you consume it.
Consistent training adherence over 12 weeks drove the real gains in this study, not supplement timing.
A convenient protein source — whether a shake after the gym or casein before bed — can still help people reach their daily target if their diet otherwise falls short, even if the specific timing itself isn't the deciding factor.

This study focused on untrained older men over 12 weeks; results in women, younger adults, or longer training periods may differ, and anyone with specific health or dietary conditions should consult a qualified professional before changing their supplement routine.