Author(s): GREYVENSTEIN, D., NEWBOLD, J.P., LEES, M.J., NUNES, E.A., DA COSTA, F.P., VILORIA, A.M., BAKER, E., SAMPAIO, M., CHAN, E., ZUPANCIC, Ž., BURD, N.A., MOORE, D.R., PHILLIPS, S.M., Institution: MCMASTER UNIVERSITY, Country: CANADA, Abstract-ID: 316

INTRODUCTION:
Quantifying amino acid catabolism and whole-body protein turnover in response to nutrition is essential for developing feeding strategies to support optimal anabolic potential. However, most controlled studies have examined the response to a single, isolated protein dose primarily in male cohorts; this approach fails to reflect typical multiple meal eating patterns and fails to capture protein balance over a full day. Therefore, we compared one-meal-a-day (OMAD) to a divided (SPLIT) meal frequency and examined whole-body protein turnover and amino acid oxidation in both males and females.
METHODS:
Healthy young adults (n = 24; 12F/12M) completed whole-body resistance exercise (RE) and consumed either a single protein meal (OMAD) or three evenly distributed protein meals (SPLIT), providing 1.6 g·kg⁻¹·day⁻¹; of mixed protein sources. Whole-body protein turnover was estimated from phenylalanine kinetics. We also assessed phenylalanine (Phe) hydroxylation, and leucine (Leu) oxidation over 14 h, divided into early, mid, and late postprandial windows. Whole body protein kinetics were determined using primed constant infusions of D5-Phe, D2-tyrosine, and [1-13C]Leu coupled with repeated plasma and breath sampling.
RESULTS:
Net protein balance increased relative to fasting levels similarly in OMAD (26.5 ± 1.2 Δµmol Phe·kg⁻¹·h⁻¹;, p < 0.001) and SPLIT (27.3 ± 0.9 Δµmol Phe·kg⁻¹·h⁻¹, p < 0.0001), with no difference between groups (p = 0.06). Phe hydroxylation was higher in OMAD during the early postprandial period (OMAD, 6.1 ± 1.0; SPLIT, 4.6 ± 0.6 µmol Phe·kg⁻¹·h⁻¹; p < 0.001), whereas it was higher in SPLIT during the later postprandial period (OMAD, 4.2 ± 1.1; SPLIT, 5.2 ± 0.5 µmol Phe·kg⁻¹·h⁻¹; p < 0.01). There were no between-group differences in Phe hydroxylation when averaged across the entire fed period (OMAD, 5.2 ± 0.8; SPLIT, 4.7 ± 0.4 µmol Phe·kg⁻¹·h⁻¹; p = 0.17). Leu oxidation in a subset of participants (n = 12; 8 OMAD/4 SPLIT) was higher in OMAD during the early postprandial period (OMAD, 91.1 ± 43.8; SPLIT, 51.3± 19.1 µmol Leu·kg⁻¹·h⁻¹; p = 0.01) and tended to be higher in SPLIT in the late postprandial period (OMAD, 33.4 ± 16.5; SPLIT, 63.2 ± 30.7 µmol Leu·kg⁻¹·h⁻¹; p = 0.056). There were no differences in Leu oxidation when averaged across the full fed period (OMAD, 57.2 ± 22.9; SPLIT, 58.1 ± 18.1 µmol Leu·kg⁻¹·h⁻¹; p = 0.95). No sex-based differences were observed in the measured outcomes.
CONCLUSION:
When total daily protein intake is matched, OMAD and SPLIT feeding strategies similarly increase whole-body protein balance during recovery from RE. Although OMAD transiently increases amino acid catabolism early post-feeding, cumulative oxidation across the day does not differ from SPLIT feeding. These findings indicate that differences in acute postprandial responses do not translate into a metabolic advantage when assessed over the full postprandial period with sufficient protein intake, independent of biological sex.