Dietary ecological momentary assessments: validation against food diaries and associations with health biomarkers

Background: Digital approaches that capture dietary behavior repeatedly in real-world settings may improve the monitoring of long-term lifestyle interventions while reducing participant burden and supporting self-awareness. This study developed and evaluated a low-burden dietary ecological momentary assessment (EMA) protocol to monitor Mediterranean diet adherence during the 12-month PENSA multimodal lifestyle trial in older adults at increased risk of cognitive decline. Methods: A total of 104 participants aged 60-80 years with subjective cognitive decline and APOE-ε4 carrier status were included. Daily mobile EMA prompts assessed key Mediterranean diet food groups through a rotating schedule, and participants received personalized feedback every 4 weeks. EMA-derived adherence indicators were evaluated against the Mediterranean Diet Adherence Screener, 3-day food diaries, nutrient profiles, usability data, and cardiometabolic and dementia-risk markers. Higher EMA-based adherence was also associated with lower body mass index, visceral adiposity, body fat percentage, insulin resistance, glycated hemoglobin, triglyceride-glucose index, and lifestyle-based dementia risk. The protocol showed high feasibility, with sustained completion rates and positive participant evaluations, although engagement declined modestly over time. Conclusion: These findings support dietary EMA as a feasible, scalable, and behaviorally meaningful approach for monitoring and promoting Mediterranean diet adherence in real-world lifestyle interventions, with potential value both as an assessment tool and as an active component to reinforce dietary change. The PENSA trial is registered at ClinicalTrials.gov (NCT03978052).