Protein and resistance training improve muscle strength and insulin resistance in older adults with type 2 diabetes

All groups improved physical performance and antioxidant balance, shown by higher uric acid levels and lower plasma iron. However, the protein supplementation group demonstrated significantly greater improvements in muscle strength and reduced insulin resistance compared to controls. The protein group also showed lower oxidative damage linked to heme-iron species, a marker of exercise-induced stress. Notably, pro-inflammatory cytokines (IFN-γ and IL-6) increased in the protein group, which researchers suggest may reflect normal metabolic adaptation to exercise rather than harmful inflammation. Adding synbiotic supplementation provided no additional benefits beyond protein plus resistance training alone. The finding was limited by the small sample size and short intervention duration, and results may not generalize to women or younger populations.

The protein group's reduction in insulin resistance is mechanistically important: insulin sensitivity typically declines with age and sedentary behavior in diabetes, and this combination appears to reverse that trajectory more effectively than exercise alone. The rise in IFN-γ and IL-6, often viewed as 'bad' inflammation, actually tracked with muscle-building adaptation—these cytokines are released during resistance exercise to signal muscle protein synthesis and metabolic remodeling. The synbiotic (probiotic plus prebiotic) addition failed to show benefit, surprising given that gut dysbiosis is theorized to drive inflammaging; this null result suggests the protein + training stimulus was sufficient to override microbial imbalance, or that 12 weeks was too short to observe microbiome shifts. Muscle damage markers (lactate dehydrogenase and creatine kinase) elevated in all groups, expected during resistance training, but the protein group's superior strength gains despite this suggest more efficient repair and synthesis. The triple-blind design (participants, trainers, and analysts masked) strengthens confidence, though dropout from 51 to 40 raises the possibility that those who remained were more compliant or responsive.