Provided by National University of Singapore

Prof Dean Ho before and after DELTA (2021 vs. 2024). Credit: Professor Dean Ho

Most individuals encounter their health primarily through an annual health screening, which provides a limited snapshot of their health status.

A new study by the Yong Loo Lin School of Medicine, National University of Singapore (NUS Medicine), challenges the way we think about health and longevity by seeking to understand what occurs between those assessments, focusing on function rather than static markers and tracking how physiology changes moment to moment.

Led by Professor Dean Ho, director of the Institute for Digital Medicine (WisDM) at NUS Medicine, the study took an unusual and highly personalized approach: Ho became the sole subject of the study.

The study, named DELTA, was designed around the central idea that everyone has their own biological baseline, shaped by age, stress, sleep, food, exercise and illness, and that this baseline shifts over time. To examine these changes, the team introduced a series of lifestyle interventions—including varying fasting durations, exercise routines and nutrition adjustments—while monitoring how Ho's biology responded in real time.

The regimen included around 20 hours of fasting each day, multiple 48-hour fasts, 90 minutes of strength or cardiovascular training every morning and a structured diet centered on leafy greens, seeds, olive oil, lean protein and other Mediterranean-style foods, with beverages limited to water, electrolytes, black coffee and black tea without milk or sugar.

Ho, 47, said, "We started this study to better understand what happens between annual health screenings, which most people rely on as their measure of health—to look beyond static markers and focus on how the body functions and changes in real time. We know people are different from each other, but we are also different from ourselves over time. Everyone has their own 'DELTA'—a unique, evolving set of data that reflects the fact that health is a story, not a snapshot."

Published in the journal PLOS One, the study began in mid-August 2024

and is still ongoing. Ho also wore three wearables—Whoop, Garmin and Apple Watch—for about eight months, allowing the study to track changes over a longer duration than typical consumer wearable reports. It builds on an earlier 2024 paper in PNAS Nexus that examined Ho's metabolic shifts over a long period.

In this latest paper, the DELTA study captured the body's metabolic switch in real time over very short time frames—even within minutes—revealing just how much can be missed about how efficiently metabolism responds to acute stress. Metabolic switching refers to how quickly the body can switch between burning sugar and burning fat, and faster switching usually means better metabolic flexibility.

The DELTA regimen resulted in several notable improvements:

For someone Ho's age, metabolic switching takes an average of 36–72 hours, or even longer. It often becomes less efficient with age. The study demonstrated that Ho's metabolic switching speed improved over time, from more than 24 hours to 16.5 hours. A custom artificial intelligence (AI) copilot developed by the research team also estimated Ho's biological age at around 32, nearly 15 years younger than his actual age. Biological age is typically estimated from a single snapshot of molecular or physiological markers, providing a static assessment of a person's health and disease risk at a given point in time. However, such approaches offer limited insight into how well the body can respond to and recover from stress—a key hallmark of healthy aging. Instead of relying on a single snapshot, the AI-powered healthspan copilot captures real-time molecular and physiological responses to stress to measure true biological resilience, revealing how quickly the body adapts and recovers. Ho's resting heart rate improved, falling from 65 beats per minute (bpm) to 46 bpm, which can indicate more efficient heart function and better recovery. Sleep architecture improved, with sleep shifting from past midnight to around 9 p.m., total sleep increasing from about five hours to nearly eight hours, more deep sleep and less time awake during the night. Gut microbiome health also showed positive changes, with no detectable Fusobacterium across all measurements and evidence of improved energy conservation during certain fasting periods.

Through the study, Ho and his team hope DELTA will empower individuals to engage meaningfully with their own health data, enabling them to make informed lifestyle changes instead of following generic routines or striving for a one-size-fits-all ideal. DELTA builds on a longevity landscape where many existing approaches—from conventional drug development to biological age clocks—continue to rely on static, snapshot-based measurements. Even when AI is incorporated, these systems often aggregate periodic data rather than capturing how the body functions and adapts in real time.

"DELTA represents a shift toward function-based longevity science by measuring physiological resilience instead of relying on static snapshots. We hope this work will not only help redefine how healthy aging is understood, but also showcase Singapore's growing role in pioneering the future of personalized longevity research," added Ho.

More information: Peter Wang et al, DELTA: Strengthening human biological resilience with an N=1 digital health and dynamic biomarker protocol, PLOS One (2026). DOI: 10.1371/journal.pone.0354234