What does that number mean?
Science only, with its sources. No opinions on this page; those live in the blog.
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What you will find here, and what you won’t.
Every entry on this page rests on published science, names its sources at the foot, and shows the date it was last reviewed. Where researchers disagree, we show both sides and the evidence each has, and we don’t pick a winner: not between keto and plant-based, not between the energy-balance and the carbohydrate-insulin accounts of weight, not between supplements. Nothing here tells you what your own numbers mean for your health; that is a conversation for Eir in the app, with your data, and for your doctor. Our founder and the people who work on Vitality Tracker have opinions on all of it. They publish them in the blog, labeled as opinion, and nowhere on this page.
What Vitality Tracker measures, calculates and asks of you.
Every biomarker, every score, every lab test and every sensor, by the health domain it belongs to, with how much a consumer device can be trusted on it and how to measure it well.
BF%Visceral fat indexVFIHow to use a bioimpedance scaleTDEEProtein, fat and carbohydrateRPEProtocols: log the things you do to yourselfHbA1cTime in rangeTIRMetabolic ageHRVOvernight resting heart rateRHRBlood pressureBPSHITotal sleepTSTCapacity: how much you can take on todaySRIEating window: first and last mealTREChronotype and circadian alignmentMCTQTREProtocols: log the things you do to yourselfSick days, holidays and unusual periodsSame time, same wayWhat the field said last week.
Every episode, paper and article covered in Last Week: Longevity, indexed by topic, by expert and by claim, with a link to the original every time. We report who said what; we don’t endorse it. Members can see where the experts agree and where they don’t.
The first issue goes out at the end of 2026; this section fills from then.
Topics, explained from the ground up.
Longer reads on a subject rather than a measure: what the evidence supports, what it doesn’t, and what is still open.
Vitality Tracker describes and tracks physiological measures recorded by your own consumer devices against your own history, for general wellness and for discussion with a health professional. It does not diagnose, predict or monitor any disease.