Effects of resistance exercise and whey protein supplementation on metabolic flexibility and glucose homeostasis in healthy older men

Rationale: Sarcopenia is associated with metabolic dysfunction. This study investigated the effects of resistance exercise (RE) and whey protein supplementation (WP) on metabolic flexibility (MF) and glucose homeostasis in healthy older men (60-80yrs). Methods: In a pooled-group analysis from a previous 4-arm randomised, double-blind, placebo-controlled trial1 , 33 healthy older men (age: 67±1yrs; BMI: 25.4±0.4 kg/m2 ) were pooled to either RE (2 /week; n¼17) or no exercise (NE; n¼16), and either WP (2 25g/d whey protein isolate; n¼17) or control (CON, 2 23.75g maltodextrin/d; n¼16) for 12weeks. A sub-analysis was also conducted between RE+CON (n¼8) and RE+WP (n¼9). At baseline and 12 weeks, participants resided in whole-room indirect calorimeters2 under highly-controlled conditions for 24-h for measurement of MF (defined as the difference between non-sleep and sleeping non-protein respiratory quotient (npRQ))3 , fasting plasma glucose and insulin concentration, insulin resistance (homeostatic model assessment of insulin resistance (HOMA-IR)) and insulin sensitivity (quantitative insulin sensitivity check index (QUICKI)), and 24-h mean interstitial glucose and 24-h glucose variability. Results: Compared to NE, RE significantly improved MF (+0.001±0.005 vs +0.022±0.004, p¼0.01), which was driven by a decrease in sleeping npRQ (-0.019±0.007, p¼0.02) rather than changes in non-sleep npRQ (+0.003±0.005, p¼0.48). No significant differences occurred between RE and NE for any other outcomes (p0.21). Compared to CON, WP tended to increase QUICKI (-0.01±0.01 vs +0.02±0.01, p¼0.06) and significantly decreased fasting plasma insulin concentration (+1.0±1.2 vs -2.3±1.1mU/L, p¼0.05), but no effects were observed on MF (p¼0.39). No differences occurred between RE+CON and RE+PRO for any outcome (p0.41). Conclusion: In healthy older men, RE significantly improves MF without effects on glucose homeostasis. Whilst WP did not affect MF, insulin sensitivity tended to improve. No synergistic effects occurred. References: 1. Griffen et al. (2022). Effects of resistance exercise and whey protein supplementation on skeletal muscle strength, mass, physical function, and hormonal and inflammatory biomarkers in healthy active older men: a randomised, double-blind, placebo-controlled trial. Experimental Gerontology, 158, 111651. 2. Griffen et al. (2022). Changes in 24-h energy expenditure, substrate oxidation, and body composition following resistance exercise and a high protein diet via whey protein supplementation in healthy older men. Physiological Reports, 10 (11), e15268. 3. Peterson et al. (2017). Eight weeks of overfeeding alters substrate partitioning without affecting metabolic flexibility in men. International Journal of Obesity, 41 (6), 887e893. Disclosure of Interest: None declared