More Protein for Diabetic Sarcopenia? One Small Trial

For older adults living with both type 2 diabetes and sarcopenia, the standard protein target may be too low to preserve muscle function. In a small 12-week randomized trial, people assigned to 1.2–1.5 g of protein per kilogram of body weight daily maintained knee strength and fatigue resistance, while those assigned to 0.8–1.0 g/kg/day declined on isokinetic testing. The result deserves attention because the endpoint was measured on a dynamometer, not guessed from a questionnaire. It also needs restraint: the trial enrolled only 30 people, reported no blinding, and never measured kidney function.

That last omission matters. Diabetes raises the likelihood of kidney disease, and a higher-protein diet is not a universal upgrade button. It may be reasonable to discuss for an older adult with documented sarcopenia and normal renal testing, but it is not something to start blindly when kidney status is unknown.

The trial tested muscle performance, not a protein theory

Kalyva et al. (2026) randomly assigned 30 older adults with confirmed type 2 diabetes and sarcopenia to either 1.2–1.5 g/kg/day of dietary protein or 0.8–1.0 g/kg/day for 12 weeks. Each group had 15 participants. The investigators measured peak torque in the knee extensors and flexors at 60°/second and 180°/second, then measured fatigue during 20 maximal contractions at 180°/second.

Participants in the higher-protein group maintained extensor and flexor peak torque at both testing speeds. Participants in the standard-protein group had statistically significant declines in those measures, with reported p values below 0.05. The standard-protein group also worsened on the fatigue index. The fatigue result showed a statistically significant group-by-time interaction and a statistically significant difference between groups at week 12, again reported as p<0.05.

The publication does not provide an effect size or confidence interval for those torque changes in the available reporting. That limits how precisely readers can judge the size of the benefit. Still, this was a more objective outcome than self-reported ability to climb stairs or rise from a chair. Isokinetic dynamometry measures force during controlled movement at a set speed. It does not tell us whether participants fell less often, stayed independent longer, or lived longer. It does show that the lower-protein group lost measurable knee performance over three months while the higher-protein group did not.

The study supports a narrow conclusion: in this small group of older adults with type 2 diabetes and sarcopenia, 1.2–1.5 g/kg/day preserved measured knee performance better than 0.8–1.0 g/kg/day over 12 weeks.

Why a healthy-adult protein target may miss this group

The general protein RDA of 0.8 g/kg/day was developed from nitrogen-balance work in metabolically healthy adults. Older adults often need more dietary protein to produce the same muscle-building response as younger adults, a phenomenon called anabolic resistance. Type 2 diabetes adds insulin resistance, which can impair post-meal amino-acid handling by muscle. The combination gives the trial result a plausible biological basis, but plausibility is not proof of an optimal dose.

Guidance from ESPEN and the PROT-AGE study group already places many older adults with chronic illness in the 1.2–1.5 g/kg/day range. That guidance was not built on dose-finding trials specifically in people with both type 2 diabetes and sarcopenia. The Kalyva trial is direct evidence in that population, but one small trial cannot establish that the range is best for every patient.

A cell-culture study by Le Bacquer et al. (2021) helps only with broad background. In C2C12 mouse myotubes, rimonabant promoted protein synthesis through a CB1-independent mechanism. It did not test dietary protein, older people, diabetes, or clinical muscle function. Its introductory discussion describes sarcopenia in terms of altered protein homeostasis, lipid accumulation, and anabolic resistance; the experiment itself cannot validate a dietary prescription.

Exercise evidence points in the same direction, with an important catch

The broader evidence base is more encouraging than the single diabetes trial, but less specific. A 2023 systematic review and meta-analysis by Cuyul-Vásquez et al. found that whey protein supplementation paired with resistance exercise improved skeletal muscle mass and strength in older adults with sarcopenia.

Every included study paired supplementation with structured resistance training. That design answers a practical question—whether protein plus training can help—but it cannot separate the effect of protein from the effect of exercise. The review also did not report a type 2 diabetes subgroup. It supports the idea that adequate protein belongs beside resistance exercise when an older person can train safely; it does not prove that whey or any higher protein target alone will reproduce those results in diabetic sarcopenia.

The body-composition result raises questions

In the 12-week diabetes trial, fat-free mass remained stable in both groups. Fat mass fell only in the higher-protein group, despite no reported difference in total calorie intake. Blood pressure stayed stable in both groups.

The fat-mass finding is difficult to interpret. With no reported calorie difference, no change in fat-free mass, and no reported change in body mass, the pattern could reflect unmeasured differences in diet adherence, physical activity, or metabolism between randomized groups. It does not erase the dynamometry result, but it weakens confidence that protein intake was the only meaningful difference between the groups.

The kidney question is unresolved

The central trial reported no estimated glomerular filtration rate, serum creatinine, or urine albumin-to-creatinine ratio at baseline or during follow-up. It also did not report baseline eGFR values or say whether chronic kidney disease was an exclusion criterion. A 12-week study would be short for detecting progressive loss of kidney function even if it had collected those measurements. Without them, it cannot answer the safety question at all.

Evidence from kidney disease does not prove that higher protein harms a diabetic older adult with normal renal function. It does show why renal status changes the discussion. In a randomized trial of adults with stage 3–4 chronic kidney disease who did not have diabetes, Hamidianshirazi et al. (2023) found that structured renal diet therapy plus nutrition education improved eGFR. The intervention involved renal-protective protein calibration, not protein augmentation. Its population and diet differ substantially from the Kalyva trial, so it cannot estimate the renal effect of 1.2–1.5 g/kg/day in type 2 diabetes. It does establish that dietary management can alter renal trajectories in people with kidney disease.

A 2022 study by Johnson et al. adds a narrower caution. In adolescents with type 1 diabetes, several tubular-injury biomarkers, including NGAL, copeptin, IL-18, and KIM-1, were associated cross-sectionally with intrarenal hemodynamic dysfunction. Adolescents with type 1 diabetes are not older adults with type 2 diabetes, and a cross-sectional biomarker association does not establish the mechanism or safety of a higher-protein diet. The study does illustrate why apparently normal routine kidney measures may not capture every aspect of diabetic renal vulnerability.

What to do with this evidence

For an older adult with type 2 diabetes, confirmed sarcopenia, normal renal function, and no significant albuminuria, the evidence supports a clinician-supervised conversation about moving from roughly 0.8–1.0 g/kg/day toward 1.2–1.5 g/kg/day. Resistance exercise should be part of that conversation when physically tolerated, because the strongest broader evidence pairs protein with training.

For anyone with chronic kidney disease, significant albuminuria, or unknown kidney status, self-prescribing a high-protein target is premature. Get baseline renal testing and individual guidance on protein intake. The trial offers a useful signal about knee performance, not a kidney-safety clearance. Its most practical lesson is simple: in diabetic sarcopenia, protein targets and renal monitoring belong in the same appointment.