Adherence to β-hydroxy-β-methylbutyrate-Enriched Oral Nutritional Supplements Enhances Survival and Nutritional Recovery in Malnourished Outpatients: Prognostic Insights

<b>Background</b>: Disease-related malnutrition (DRM) in outpatients is associated with increased mortality and functional decline. Morphofunctional assessments, including phase angle (PA), rectus femoris cross-sectional area (RF-CSA), and handgrip strength (HGS), provide valuable prognostic insights in the ambulatory setting. Nutritional recovery programs enriched with β-hydroxy-β-methylbutyrate (HMB) offer potential benefits in improving nutritional and functional outcomes. <b>Objective</b>: To evaluate the effects of a six-month nutritional recovery program combining HMB-enriched oral nutritional supplements (HMB-ONS), dietary recommendations, and exercise on survival, morphofunctional markers, and adherence in malnourished outpatients. <b>Methods</b>: This retrospective observational study included 135 malnourished outpatients diagnosed using GLIM criteria. Morphofunctional assessments included PA (bioimpedance analysis), RF-CSA (nutritional ultrasound), HGS (dynamometry), and the Timed Up and Go (TUG) test. Adherence was assessed using pharmacy retrieval records and a validated questionnaire. Changes in morphofunctional markers and their association with mortality were analyzed using multivariate Cox regression models. <b>Results</b>: After six months, significant improvements were observed in PA (+0.47°), RF-CSA (+0.90 cm²), HGS (+4.1 kg), and TUG (-0.93 s) (all <i>p</i> < 0.001). These improvements were more pronounced in the high-adherence group, which also exhibited a reduced mortality risk (HR 0.42, <i>p</i> < 0.05). Changes in PA and HGS were strongly associated with survival, with ΔPA showing an HR of 0.27 (95% CI: 0.15-0.50, <i>p</i> < 0.001) and ΔHGS showing an HR of 0.82 (95% CI: 0.75-0.89, <i>p</i> < 0.001). <b>Conclusions</b>: A nutritional recovery program with HMB-ONS significantly improves survival and morphofunctional markers in malnourished patients, with the greatest benefits observed in those with high adherence. These findings underscore the importance of adherence-support strategies in optimizing clinical outcomes and highlight the need for further research to confirm long-term benefits.