Effects of 8 weeks of resistance training in combination with a high protein diet on body composition, muscular performance, and markers of liver and kidney function in untrained older ex-military men

Reza Bagheri; Abolfazl Shakibaee; Donny M Camera; Vahid Sobhani; Hamid Ghobadi; Eisa Nazar; Hadi Fakhari; Fred Dutheil

doi:10.3389/fnut.2023.1205310

Effects of 8 weeks of resistance training in combination with a high protein diet on body composition, muscular performance, and markers of liver and kidney function in untrained older ex-military men

Front Nutr. 2023 Jun 29:10:1205310. doi: 10.3389/fnut.2023.1205310. eCollection 2023.

Authors

Reza Bagheri¹, Abolfazl Shakibaee¹, Donny M Camera², Vahid Sobhani¹, Hamid Ghobadi³, Eisa Nazar⁴, Hadi Fakhari⁵, Fred Dutheil⁶

Affiliations

¹ Exercise Physiology Research Center, Lifestyle Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran.
² Department of Health and Biostatistics, Swinburne University, Melbourne, VIC, Australia.
³ Department of Exercise Physiology, Ferdowsi University of Mashhad, Mashhad, Iran.
⁴ Psychiatry and Behavioral Sciences Research Center, Addiction Institute, Mazandaran University of Medical Sciences, Sari, Iran.
⁵ Department of Exercise Physiology, University of Isfahan, Isfahan, Iran.
⁶ CNRS, LaPSCo, Physiological and Psychosocial Stress, CHU Clermont-Ferrand, University Hospital of Clermont-Ferrand, Preventive and Occupational Medicine, Université Clermont Auvergne, Clermont-Ferrand, France.

Abstract

Background: The effects of a high protein diet in combination with chronic resistance training (RT) on skeletal muscle adaptation responses in untrained older ex-military men is unknown. Therefore, we compared the effects of 8 weeks of RT in combination with either a high (1.6 g/kg/d) or low protein diet (0.8 g/kg/d) on body composition [skeletal muscle mass (SMM) and body fat percentage (BFP)], muscular strength, power, and endurance (upper and lower body), markers of liver [alanine transaminase (ALT), aspartate aminotransferase (AST), and gamma-glutamyl transferase (GGT)] and kidney (creatinine and urea) function, and lipid profile low-density lipoprotein (LDL), high-density lipoprotein (HDL), and cholesterol levels in a cohort of healthy, untrained older ex-military males.

Methods: Forty healthy untrained older ex-military males (age: 61 ± 2 yr, body mass index: 23.2 ± 1.3 kg.m^-2) performed 8 weeks (three sessions·w^-1) of RT with either 1.6 g/kg/d (RHP; n = 20) or 0.8 g/kg/d of protein (RLP; n = 20). Body composition (assessed by Inbody 720), muscular strength (1-RM for chest and leg press), power (Wingate test), endurance (75% 1-RM for chest and leg press), and markers of liver and kidney function (biochemical kits) were assessed pre and post-intervention.

Results: SMM and muscular strength (upper and lower body) increased post-intervention in both groups and were significantly greater in RHP compared to RLP, while muscular power increased to the same extent in both groups (p < 0.05) with no between-group differences (p > 0.05). In contrast, there were no post-intervention changes in muscular endurance, HDL, and BFP remained in either group (p > 0.05). ALT and creatinine significantly increased in RHP compared to RLP while GGT, AST, and urea only increased in the RLP group (p < 0.05). LDL and cholesterol significantly decreased in both groups (p < 0.05).

Conclusion: A daily intake of 1.6 g/kg/d protein was superior to 0.8 g/kg/d (current recommended daily intake) for promoting greater improvements in SMM and muscle strength and thus may be a more suitable level of intake for promoting such adaptive responses. Notwithstanding observed between-group differences in ALT and creatinine and the fact that levels remained within normal ranges, it is feasible to conclude that this daily protein intake is efficacious and well tolerated by healthy, untrained older ex-military males.

Keywords: aging; nutrition; protein; resistance exercise; skeletal muscle adaptation.