Effects of Higher Dietary Protein Intake on Isokinetic Muscle Performance in Older Adults with Type 2 Diabetes...

Background: Type 2 diabetes mellitus (T2DM) is linked to accelerated losses in muscle function. The aim of the present investigation was to evaluate the effect of chronic higher-protein intake on isokinetic knee performance in the older adults with type 2 diabetes mellitus (T2DM). Methods: Thirty adults (15 men and 15 women) aged 60-80 years with non-insulin-treated T2DM and sarcopenia-related deficits were randomized for 12 weeks to a higher-protein diet (1.2-1.5 g·kg^-1·day^-1) or a recommended protein diet (0.8-1.0 g·kg^-1·day^-1), with meal plans designed to maintain body mass. Protein was increased mainly through Mediterranean-style protein sources while diet was monitored using repeated 3-day recalls. Isokinetic knee extensors and flexors peak torque (angular velocity 60°/s) was assessed at baseline and at week 6 and at the end of the 12th week of intervention. Fatigability (20 maximal contractions at an angular velocity at 180°/s) and DXA body composition were assessed at baseline and at the end of the 12th week of intervention. Data were analyzed using two-way repeated-measures ANOVA with repeated measures on time (2 groups × 3 time points), followed by post hoc analysis when significant difference was occurred. Results: Thirty participants completed the trial. Energy intake and body mass remained stable in both groups. At the end of week 12, peak torque declined in the control group (p < 0.05) but remained stable in the higher-protein group. The fatigue index worsened over time in controls but was preserved in the higher protein group, resulting in a significant group d7 time interaction at week 12 (p < 0.05) (post hoc between-group difference at week 12, p < 0.05). Fat-free mass and blood pressure did not change. In fat mass, a decrease was observed with higher protein intake, whereas it remained stable in the control group. Conclusions: Higher protein intake for 12 weeks preserved knee muscle performance in older adults with T2DM without weight gain, supporting dietary protein optimization to counter functional decline.