Starting Point Matters: Baseline Protein Intake as a Moderator of the Protein-Fat-Free Mass Relationship in Energy-Restricted Athletes.

Recent research has attempted to quantify the dose-response relationship between dietary protein intake and fat-free mass preservation during energy restriction in resistance-trained individuals. While meta-regression analyses have helped identify intake ranges associated with fat-free mass retention, these models typically consider only the prescribed intervention dose. However, individuals enter dietary interventions with different baseline protein intakes, which may influence their physiological response to additional protein. We also highlight the importance of obtaining baseline dietary assessments after an appropriate dietary adaptation period, so that baseline protein intake is accurately characterized before the intervention begins. Ignoring this starting point may therefore obscure important heterogeneity in responsiveness across studies. In this Current Opinion, we discuss the potential role of baseline protein intake as a moderator of the protein-fat-free mass relationship and explore how accounting for baseline intake may alter the interpretation of protein dose-response models. We also present exploratory evidence suggesting that higher baseline protein intakes may be associated with diminishing returns in fat-free mass preservation. Considering baseline protein intake may help refine future research designs and support more individualized protein intake recommendations during energy restriction.