The gut microbiome significantly influences long-term health, akin to physical fitness. As individuals age, the balance of microbial populations shifts unfavorably—one of the early detriments of aging. By the time someone reaches their mid-30s, meaningful changes become evident. Beneficial species that produce metabolites contributing to tissue function decline, while harmful species associated with chronic inflammation increase. Thankfully, interventions can restore a more youthful microbial balance. Fecal microbiota transplantation (FMT) from a young donor to an older patient is one such approach. In short-lived species, FMT improves health and extends lifespan. Although FMT is currently used in a limited clinical context, the broader availability of therapies to reverse gut microbiome aging remains uncertain. At present, self-experimenters are the primary recipients of this treatment. Research on the gut microbiome’s role in aging and neurodegenerative diseases has intensified. As the global population ages,…