Effects of Whey, Soy or Leucine Supplementation with 12 Weeks of Resistance Training on Strength, Body Composition, and Skeletal Muscle and Adipose Tissue Histological Attributes in College-Aged Males

Abstract

We sought to determine the effects of L-leucine (LEU) or different protein supplements standardized to LEU (~3.0 g/serving) on changes in body composition, strength, and histological attributes in skeletal muscle and adipose tissue. Seventy-five untrained, college-aged males (mean ± standard error of the mean (SE); age = 21 ± 1 years, body mass = 79.2 ± 0.3 kg) were randomly assigned to an isocaloric, lipid-, and organoleptically-matched maltodextrin placebo (PLA, n = 15), LEU (n = 14), whey protein concentrate (WPC, n = 17), whey protein hydrolysate (WPH, n = 14), or soy protein concentrate (SPC, n = 15) group. Participants performed whole-body resistance training three days per week for 12 weeks while consuming supplements twice daily. Skeletal muscle and subcutaneous (SQ) fat biopsies were obtained at baseline (T1) and ~72 h following the last day of training (T39). Tissue samples were analyzed for changes in type I and II fiber cross sectional area (CSA), non-fiber specific satellite cell count, and SQ adipocyte CSA. On average, all supplement groups including PLA exhibited similar training volumes and experienced statistically similar increases in total body skeletal muscle mass determined by dual X-ray absorptiometry (+2.2 kg; time p = 0.024) and type I and II fiber CSA increases (+394 μm² and +927 μm²; time p < 0.001 and 0.024, respectively). Notably, all groups reported increasing Calorie intakes ~600-800 kcal/day from T1 to T39 (time p < 0.001), and all groups consumed at least 1.1 g/kg/day of protein at T1 and 1.3 g/kg/day at T39. There was a training, but no supplementation, effect regarding the reduction in SQ adipocyte CSA (-210 μm²; time p = 0.001). Interestingly, satellite cell counts within the WPC (p < 0.05) and WPH (p < 0.05) groups were greater at T39 relative to T1. In summary, LEU or protein supplementation (standardized to LEU content) does not provide added benefit in increasing whole-body skeletal muscle mass or strength above PLA following 3 months of training in previously untrained college-aged males that increase Calorie intakes with resistance training and consume above the recommended daily intake of protein throughout training. However, whey protein supplementation increases skeletal muscle satellite cell number in this population, and this phenomena may promote more favorable training adaptations over more prolonged periods.

Keywords: leucine; resistance training; satellite cell; soy; whey.

Figure 1

Study design. Abbreviations: DXA, dual x-ray absorptiometry; 3-RM, three-repetition maximum test; IMTP, isometric mid-thigh pull.

Figure 2

CONSORT diagram of the study. Legend: Details regarding this Consolidated Standards of Reporting Trails (CONSORT) diagram can be found in the results.

Figure 3

Total volume lifted and changes in strength measures between groups. Legend: Data include total volume lifted during the 12-week training intervention (panel a) as well as pre- and post-intervention 3-repetition maximum (RM) squat values (panel b), 3-RM bench press values (panel c), and isometric mid-thigh pull (IMTP) peak force values (panel d). Each bar graph depicts group averaged data presented as mean + standard error values, and mean values are presented within each bar. Additional abbreviations: PLA, maltodextrin placebo; LEU, L-leucine; WPC, whey protein concentrate; WPH, whey protein hydrolysate; SPC, soy protein concentrate; Symbol: * within-group increase from pre- to post training (p < 0.05).

Figure 4

Changes in body composition variables and vastus lateralis muscle thickness between groups. Legend: Data include pre- and post-intervention body mass values (panel a), total fat mass values determined by dual x-ray absorptiometry (DXA; panel b), total body muscle mass (TBMM) values determined by DXA (panel c), and vastus lateralis (VL) thickness determined by ultrasonography (panel d). Each bar graph depicts group averaged data presented as mean + standard error values, and mean values are presented within each bar. Additional abbreviations: PLA, maltodextrin placebo; LEU, L-leucine; WPC, whey protein concentrate; WPH, whey protein hydrolysate; SPC, soy protein concentrate; Symbol: * within-group increase from pre- to post training (p < 0.05).

Figure 5

Changes in muscle fiber cross sectional area, myonuclear number and satellite cell counts between groups. Legend: Data include pre- and post-intervention type I and type II fiber cross sectional area (CSA) values (panels a,b), type I and type II fiber myonuclear number values (panels c,d), and total satellite cell counts (panel f). Due to poor tissue quality on select subjects, n-sizes were as follows: PLA n = 13, LEU n = 13, WPC n = 15, WPH n = 12, and SPC n = 14. Representative 20× objective histology images from one subject demonstrating myofiber hypertrophy and increases in satellite cell counts are presented in (panels e,g), respectively. Each bar graph depicts group averaged data presented as mean + standard error values, and mean values are presented within each bar. Abbreviations: PLA, maltodextrin placebo; LEU, L-leucine; WPC, whey protein concentrate; WPH, whey protein hydrolysate; SPC, soy protein concentrate. Symbols: * within-group increase from pre- to post training (p < 0.05); #, WPC > PLA at T39 (p < 0.05).

Figure 6

Changes in gluteal subcutaneous adipocyte cross sectional area between groups. Legend: Pre- and post-training subcutaneous adipocyte cross sectional area (CSA) values are presented in (panel a). Representative 10x objective histology images from one subject demonstrating a reduction in fat cell size is presented in (panel b). Due to poor tissue quality on select subjects, n-sizes were as follows: PLA n = 14, LEU n = 12, WPC n = 14, WPH n = 10, and SPC n = 13. The bar graph depicts group averaged data presented as mean + standard error values, and mean values are presented within each bar. Abbreviations: PLA, maltodextrin placebo; LEU, L-leucine; WPC, whey protein concentrate; WPH, whey protein hydrolysate; SPC, soy protein concentrate.