No anabolic influence of balanced vs. unbalanced meal-based protein consumption in regulating daily myofibrillar protein synthesis rates in young, healthy males and females

Background: Protein ingestion stimulates muscle protein synthesis (MPS) rates to support skeletal muscle protein mass turnover. It has been suggested that a minimal threshold of per-meal protein intake is necessary to stimulate MPS above basal rates. As such, a traditionally consumed, unbalanced eating pattern may fail to meet that anabolic threshold on multiple feeding occasions throughout the day. Therefore, the distribution and frequency of protein intake may play an important anabolic regulatory role on MPS. Objective: We aimed to determine the effect of protein distribution (balanced [BAL] and unbalanced [UBAL]) in regulating changes in daily myofibrillar protein synthesis rates during a 9-d resistance training intervention. Hypothesis: Compared to UBAL protein distribution, BAL would lead to greater daily myofibrillar protein synthesis rates. Design: During a 9-d intervention period, forty healthy, physically active males and females (25 ± 4 y; BMI=24.1 ± 2.1 kg·m -2 ) consumed a fully provided, weight-maintenance diet consisting of 1.1–1.2 g·kg -1 ·d -1 of dietary protein with either UBAL (10, 30, 60% of daily protein at meal 1, 2, and 3, respectively) or BAL (20% of daily protein at 5 eating occasions) distribution. Additionally, participants completed whole-body resistance exercises every third day. To measure daily myofibrillar protein synthesis rates, participants were loaded (5 mL·kg -1 ) with deuterated water (D 2 O) and subsequently consumed D 2 O throughout the study period (0.625 mL·kg -1 ·d -1 ). Periodic saliva samples were collected and analyzed by liquid chromatography-tandem mass spectrometry (LC/MS/MS) to determine total body water (TBW) enrichment. Muscle samples were collected from the vastus lateralis at the beginning and end of the trial and analyzed by LC/MS/MS for alanine enrichment. MPS was calculated from the change in myofibrillar protein-bound enrichments between muscle samples and TBW enrichment multiplied by 3.7. Data were analyzed using mixed effects models. Results: There were no differences in daily energy (kcals), protein (g·kg -1 ·d -1 ), carbs (%kcal), or fat (%kcal) consumed between groups (all P >0.05). Likewise, baseline strength measures (10-repetition max) and total volume of exercise during the intervention were not different (all P >0.05). Daily myofibrillar protein synthesis rates during a 9-d resistance training intervention were not different ( P >0.545) between UBAL (2.46 ± 1.36 %·d -1 ) and BAL groups (2.78 ± 1.78 %·d -1 ) Conclusions: Our results demonstrated that there is no regulatory influence of protein distribution on the stimulation of myofibrillar protein synthesis rates in young adults. This study was funded by The Beef Checkoff. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.