A test is needed to reliably indicate whether interventions like fasting, rapamycin, or metformin are working at an individual level.

“when you lift weights you can look at how much weight you're lifting you can look at your dexa scan and see how much muscle mass you're generating like those are biomarkers those are giving you outputs that say my input is good or my input needs to be modified when you take a sleep supplement you can look at your eight sleep and go oh my sleep is getting better like there's a biomarker um when you take Metformin when you take rapamycin when you fast we don't have a biomarker that gives us any insight into whether or not we're moving in the right direction”