Strategies and challenges for the recruitment of young healthy participants in the dietary approaches to longevity and health (DiAL health) pilot trial

BACKGROUND: Understanding the impact of nutrition on human aging requires long-term trials in young, healthy, unmedicated adults. As part of the Dietary Approaches for Longevity and Health (DiAL Health) pilot project, we evaluated strategies for recruiting this population for aging-related dietary intervention studies. METHODS: We analyzed recruitment costs to enroll 70 participants (ages 25-49, BMI 22.0-29.9 kg/m²) across two DiAL Health sites and used NHANES data (2017-March 2020) to estimate the proportion of U.S. adults meeting partial trial eligibility. Additionally, a formative study surveyed 492 U.S. adults (≥18 years) to assess interest in aging-focused dietary trials. RESULTS: Of 2049 applicants screened, 70 were enrolled (3.4 %), with recruitment costs of $1572 per participant at site 1 and $625 at site 2. NHANES data revealed only 3.6 % (555/15,560) of adults met partial eligibility criteria, while 2.2 % (11/492) of formative survey respondents met full eligibility. DiAL Health eligible participants were willing to participate in dietary interventions like time-restricted eating or caloric restriction, but willingness declined for longer or more burdensome trials. CONCLUSIONS: Recruiting young, healthy, unmedicated individuals for aging-focused dietary intervention trials is challenging due to low rates of eligibility and enrollment (∼3-4 % of initial applicants enrolled). Longer trials with stricter eligibility are likely to face greater recruitment barriers, highlighting the need for targeted strategies to engage, recruit, and retain this population effectively.