Should You Eat More Protein While Cutting? Common Wisdom vs. the Research

What research says

• A systematic review by Helms et al.
• (2014) of lean resistance-trained athletes under caloric restriction supports intakes of 2.0–2.4 g/kg/day for muscle retention — above the ~1.6 g/kg commonly cited for maintenance.
• During a deficit, amino acids compete with other metabolic substrates for energy use, reducing the net fraction available for muscle protein synthesis and effectively raising requirements.
• Hector & Phillips (2018) similarly recommend at least 2.0 g/kg for athletes in an energy deficit.
• The directional claim — raise protein when cutting — is well-supported.

What research says

• Research comparing rate of weight loss with lean mass outcomes — including Barakat et al.
• (2020) and similar work — generally finds that slower deficits (~0.5–1% body weight per week) preserve more lean mass than aggressive cuts exceeding 1% per week.
• Rapid weight loss tends to amplify lean mass loss alongside fat loss, and adverse hormonal effects (decreases in testosterone and IGF-1) have been reported.
• That said, study protocols and populations vary enough that the evidence is directionally consistent but not conclusive.

What research says

• Churchward-Venne et al.
• (2012) demonstrate that fast-digesting, high-leucine proteins like whey elicit a stronger acute muscle protein synthesis (MPS) response.
• However, when total protein intake is equated across meal and daily timescales, differences between protein sources tend to narrow in most studies.
• Plant proteins have a different essential amino acid profile, but this can be addressed by increasing total quantity or combining sources.
• The prevailing research view is that hitting an adequate total intake is the primary priority during a caloric deficit, with source optimization as a secondary consideration.