Westlake Frequent-sampling Cohort 2

This observational follow-up study extends a previously completed 15-day intensive longitudinal study (WeF) of the gut microbiome in healthy adults. The objective of WeF2 is to characterize the long-term stability and dynamics of the gut and oral microbiota in the same cohort across multiple timescales, and to determine whether the day-to-day variability patterns observed at baseline persist over months and years. Participants who completed the WeF baseline protocol will be invited to attend periodic follow-up visits for low-frequency biospecimen collection and to repeat the original 15-day high-frequency sampling protocol at planned intervals, beginning approximately six months after the WeF baseline and continuing at extended intervals thereafter. By combining sparse routine sampling with recurring high-density sampling windows, the study aims to distinguish the stable core microbiome from transient and seasonal fluctuations, to track gradual community shifts under free-living conditions, and to further explore relationships among microbiome dynamics, dietary intake, and host glycemic regulation over an extended observation period.