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

## TL;DR

A 12-week higher-protein diet helped preserve knee muscle performance in older adults with type 2 diabetes without causing weight gain.

## Contribution

Demonstrates that higher dietary protein preserves muscle function in older adults with T2DM.

## Key findings

- Higher-protein intake preserved isokinetic knee performance while control group showed decline.
- Fat-free mass remained stable and fat mass decreased in the higher-protein group.
- Fatigability improved in the higher-protein group compared to controls.

## Abstract

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.