This study aimed to evaluate the effect of an Intervention Food for Special Medical Purposes (FSMP) on the nutritional status and muscle function of middle-aged and older adults at risk of malnutrition.

A multicenter, randomized, active-controlled, parallel-group study.

Two clinical centers located in China.

135 adults aged 45–80 years at risk of malnutrition (Mini Nutritional Assessment [MNA] score ≤ 23.5).

Participants were randomized to one of three groups for a 12-week nutritional intervention: Intervention FSMP (one daily sachet of a novel high-protein FSMP plus dietetic counseling); Active Control (one daily sachet of an established FSMP plus dietetic counseling); and Control (dietetic counseling alone). The primary outcome was the change in MNA score. Secondary outcomes were body weight, handgrip strength, calf and mid-upper arm circumferences, and SARC-F score.

Linear mixed-effects models showed significant group-by-time interactions for MNA score, body weight, BMI, handgrip strength, and calf circumference. At week 12, both FSMP groups demonstrated greater improvements in MNA score compared with Control (Intervention FSMP: adjusted difference 2.3, 95% CI 1.4–3.2; Active Control: adjusted difference 3.1, 95% CI 2.2–4.0; both P < 0.001). The between-FSMP comparison for MNA was not statistically significant (adjusted difference −0.8, 95% CI −1.7 to 0.1; P = 0.087). The Intervention FSMP group showed greater gains in body weight than Control (adjusted difference 1.2 kg, 95% CI 0.8–1.7; P < 0.001). Compared with Control, handgrip strength improved in both FSMP groups (adjusted differences 2.2–3.0 kg for left hand and 2.8 kg for right hand; all P < 0.001). Across groups, no significant differences were noted in adverse events and gastrointestinal tolerability.

Targeted 12-week nutritional intervention with a high-protein FSMP was associated with improvements in nutritional status and handgrip strength in adults at risk of malnutrition.