The DELTA protocol: three draws around a defined 48-hour fast turn a static number into a response curve. Here is the reasoning, and the safety screen.
A single adaptive-age number is a snapshot. It tells you where you are, not how you respond. The DELTA protocol exists to answer the second question: three blood draws bracketing a defined 48-hour fast — one before, one at the end of the fast, one after refeeding — and the deltas between them become your response curve.
Fasting is one of the few physiological stresses you can apply with a defined start, a defined end, and a defined protocol. Glucose, insulin, and inflammatory markers (CRP among them) all move through a fast in documented ways — the metabolic switch from glucose to fatty-acid-derived ketones is typically described as engaging somewhere between 12 and 36 hours of fasting in the review literature (Anton et al., "Flipping the Metabolic Switch", Obesity 26(2), 2018).
One draw shows the switch's shadow. Two draws show direction. Three draws — before, fasted, refed — show how your system absorbs the stress and recovers from it. That recovery shape is the DYNAMICS signal, and it is the part you can actually influence this quarter, unlike the multi-year LEVEL gap.
Each draw is read as a standard panel and scored with the same deterministic PhenoAge arithmetic (Levine et al., 2018). Nine markers, chronological age, sex. No model in the loop, no unit coercion — if a lab reports a marker in an unfamiliar unit, it is rejected rather than converted.
And one thing Delta will never do: turn the response curve into dosage advice. "Your number dropped 1.2 years during the fast, so fast more often" is exactly the kind of inference we refuse to draw. The curve is information for you and your clinician, not a prescription.
A 48-hour fast is a genuine physiological stress test, and for some people it is a genuinely bad idea. Delta's safety screen refuses to schedule the protocol for:
The app does not soften this into a "check with your doctor first" banner. A block is a block. The clinical exclusions above mirror standard contraindications for prolonged fasting trials, and the cost of over-blocking one interested user is far lower than the cost of under-blocking the wrong one.
Three draws means three panel photos. Each is sent to Delta's analyzer to be read, then discarded — the analyzer keeps nothing. Scores, curves, and history live on your device. No account, no server-side profile, nothing sold, nothing used for advertising.
If you want the long version of the underlying biomarker model, read Levine et al. 2018, "An epigenetic biomarker of aging for lifespan and healthspan", Aging 10(4). The fasting-metabolism review is Anton et al. 2018, Obesity 26(2). Both are open access.
Care decisions stay between you and your clinician. Delta is a wellness product — it measures honestly, blocks where blocking is due, and stops there.
