Exactly How Much Protein You Need to KEEP Muscle While Dieting (New Meta-Analysis)

When you're dieting to lose fat, the biggest fear is losing hard-earned muscle in the process. So how much protein do you really need to preserve lean mass while cutting?

A new 2025 meta-analysis by Refalo et al. has finally given us clear, evidence-based answers. Let’s break it down so you can get results without losing muscle.

Why This Matters

Losing fat without losing muscle is the holy grail of body composition. But protein recommendations during dieting have always varied. Should you scale to body weight or lean mass? Should leaner people eat more?

For years, ~1.6g/kg/day was the common guideline. But new research shows that number may be too low, especially for trained, lean individuals.

The Study at a Glance

In 2025, Refalo and colleagues published a meta-regression analyzing:

• 31 studies

• Over 700 resistance-trained participants

• All undergoing fat loss phases

They looked at protein intake relative to both total body weight and fat-free mass.

Key Findings

• Up to 1.9g/kg/day of body weight significantly reduced muscle loss.

• Up to 2.5g/kg/day of lean mass showed similar benefits.

• Even higher intakes (up to 3.2g/kg body weight or 4.2g/kg lean mass) continued to show linear improvements in fat-free mass retention.

Lean individuals, males, and those dieting aggressively benefited most from higher intakes.

Nuances and Limitations

• Fat-free mass includes more than muscle tissue

• Measurement methods varied across studies

• Diminishing returns past ~2.5–3.5g/kg/day, but no downside observed

Bottom line: More protein generally helped, but there’s no need to overcomplicate exact targets.

Practical Recommendations

Here’s what we suggests based on the latest research:

• General fat loss clients: 1.8–2.7 g/kg/day

• Leaner or aggressively cutting individuals: Up to 3.5 g/kg/day

• Don’t stress about scaling to fat-free mass unless you’re competing or very precise with data

Protein is your insurance policy. Use it wisely.

Final Thoughts

This new analysis confirms what advanced coaches have seen anecdotally:

• Higher protein preserves muscle during fat loss

• Leaner, more advanced athletes need even more

If you’re in a cut, dial in your protein to keep your gains.

Scientific Reference:

Refalo, M. C., Trexler, E. T., & Helms, E. R. (2025). Effect of dietary protein on fat-free mass in energy-restricted, resistance-trained individuals: An updated systematic review with meta-regression. Strength and Conditioning Journal, 47(3), 10–20.

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