Hypothesis

A personalized fasting regimen, calibrated to an individual's baseline MileAge and tissue‑specific metabolomic signatures, will produce greater autophagic flux (measured by LC3‑II/I ratio in circulating extracellular vesicles) and improve cardiovascular fitness (VO₂ Max) and lipid profile (ApoB < 80 mg/dL) without accelerating telomere attrition compared to a standard 24‑hour intermittent fasting schedule.

Mechanistic Rationale

It's known that prolonged fasting activates AMPK‑ULK1 and SIRT2‑ATG4B pathways, driving autophagy after ~24 h, while mTOR inhibition sustains the response up to 48 h [1][2]. However, AMPK versus SIRT2 dominance remains debated, and tissue‑specific responses vary widely [3][4]. MileAge, a plasma NMR‑derived metabolomic clock, predicts mortality better than many traditional biomarkers [5] and reflects metabolic aging that likely correlates with cellular nutrient‑sensing capacity. We propose that individuals with a high MileAge delta (i.e., biologically older metabolism) possess a blunted AMPK response but retained SIRT2 activity, making them responsive to fasting protocols that emphasize SIRT2‑mediated LC3 processing (e.g., longer fasts with modest calorie density). Conversely, those with low MileAge may rely more on AMPK‑ULK1 activation and benefit from shorter, more frequent fasts.

Nutrient‑dense caloric restriction improves insulin sensitivity and reduces visceral fat, yet early telomere loss suggests a stress‑response trade‑off [9][10][11]. By aligning fasting duration with MileAge‑guided AMPK/SIRT2 balance, we hypothesize that autophagic clearance can be achieved without triggering the DNA‑damage response that accelerates telomere shortening.

Predictions

1. Participants assigned to the MileAge‑guided fasting arm will show a significantly higher LC3‑II/I ratio in plasma‑derived extracellular vesicles after 4 weeks than those on a fixed 24‑h intermittent fast.
2. VO₂ Max will increase ≥5 % and ApoB will drop below 80 mg/dL in the personalized arm, while remaining unchanged in the control.
3. Telomere length change (measured by qPCR) will not differ significantly between groups, indicating that personalized fasting avoids the early telomere attrition seen with unguided caloric restriction.
4. MileAge delta will decrease more in the personalized arm, reflecting metabolic rejuvenation.

Experimental Design

A randomized, parallel‑group trial with 120 adults (aged 30‑60, BMI 25‑35) will stratify participants by baseline MileAge delta (high vs low). Within each stratum, subjects receive either:

• Personalized fasting: fasting duration (18‑36 h) and frequency (2‑4 times/week) set according to an algorithm that weights MileAge, baseline VO₂ Max, and ApoB; meals during eating windows are nutrient‑dense (≥30 % protein, micronutrient‑rich).
• Standard intermittent fasting: 24‑h fast twice weekly with ad libitum nutrient‑dense eating windows.

Primary outcomes: LC3‑II/I ratio in extracellular vesicles (Western blot), VO₂ Max (cardiopulmonary exercise test), ApoB (enzymatic assay), telomere length (qPCR), and MileAge shift (plasma NMR). Measurements at baseline, week 4, and week 12.

Statistical plan: mixed‑effects models testing group × time interactions; α = 0.05.

Potential Outcomes

If the hypothesis holds, personalized fasting will decouple autophagy activation from telomere stress, offering a safer, more effective longevity strategy. Failure to observe differential autophagy or telomere effects would suggest that MileAge does not capture the AMPK/SIRT2 balance relevant to fasting response, prompting a search for alternative metabolic predictors.

References

[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC10509423/ [2] https://int.livhospital.com/hours-of-fasting-for-cell-repair/ [3] https://academic.oup.com/edrv/article/46/6/856/8211151 [4] https://doi.org/10.1101/2025.04.13.648650 [5] https://pmc.ncbi.nlm.nih.gov/articles/PMC11654675/ [6] https://longevity.technology/news/5-biomarkers-that-can-predict-your-lifespan/ [7] https://www.hindustantimes.com/lifestyle/health/longevity-specialist-shares-5-biomarkers-that-can-predict-how-long-you-will-live-and-the-quality-of-your-overall-health-101764498524390.html [8] https://pmc.ncbi.nlm.nih.gov/articles/PMC5315691/ [9] https://pmc.ncbi.nlm.nih.gov/articles/PMC3014770/ [10] https://www.psu.edu/news/health-and-human-development/story/calorie-restriction-study-reveals-complexities-how-diet-impacts [11] https://www.aging-us.com/article/100581/text