Most individuals learn about their health through occasional doctor visits and annual blood tests. While helpful, these snapshots only reflect the body’s state at a single moment in time.
Researchers at the National University of Singapore are investigating an alternative approach: understanding health by observing daily changes and recovery patterns in the body.
This project, known as DELTA, is highly personal. Professor Dean Ho, director of the Institute for Digital Medicine at the Yong Loo Lin School of Medicine, served as the sole participant.
His team continuously monitored his body while he altered his diet, exercise routine, fasting periods, and sleep habits.
The core idea of DELTA is that each person’s biological baseline isn’t static. Factors like sleep, stress, diet, physical activity, illness, and age can cause daily fluctuations in how the body functions. Even the same person might respond differently to the same challenge at different times.
The study began in August 2024 and is ongoing. Over approximately eight months, Ho wore three consumer health devices—a Whoop tracker, a Garmin smartwatch, and an Apple Watch—which provided repeated data on heart rate, activity levels, recovery metrics, and sleep patterns.
He also made significant lifestyle changes. Ho frequently fasted for about 20 hours daily and completed several 48-hour fasts. Each morning, he engaged in about 90 minutes of strength or cardio workouts.
His diet centered on leafy greens, seeds, olive oil, lean proteins, and other foods typical of a Mediterranean diet. Beverage intake was mainly water, electrolytes, black coffee, and black tea—without milk or sugar. It’s important to note this was a personalized experiment, not a public health recommendation.
A key focus was metabolic flexibility—the body’s ability to switch efficiently between using carbohydrates and fats for energy depending on fasting, activity, or food intake. Researchers tracked how quickly Ho transitioned from primarily burning sugar to relying on stored fat.
Results showed his switching time improved during the study. Initially taking over 24 hours, it decreased to approximately 16.5 hours, indicating a more responsive metabolism.
His resting heart rate also dropped significantly—from about 65 beats per minute to 46—suggesting enhanced cardiovascular fitness, though interpreting this value depends on individual health contexts, symptoms, and medications.
Sleep patterns changed markedly. Ho shifted his bedtime from after midnight to around 9 p.m., with sleep duration increasing from roughly five hours to nearly eight, including more deep sleep and fewer nighttime awakenings.
The team analyzed Ho’s gut microbiome—the community of microbes in his digestive system—and noted positive changes, such as the absence of Fusobacterium, a potentially harmful bacterium. The data also indicated shifts in how his body conserved energy during fasting periods.
An AI system was employed to analyze the vast amount of data, acting as a health ‘copilot’ to assess how his body responded and recovered from stress. Remarkably, the system estimated his biological age to be around 32, even though he was 47.
Biological age attempts to gauge how old the body appears based on measurable biological markers, not simply years since birth. Many such systems focus on a single set of blood, genetic, or physiological indicators. DELTA researchers emphasize that observing how quickly and effectively the body responds and recovers offers additional insights into healthy aging.
This concept of resilience—how quickly and effectively one recovers from stress—is central to the project. Two people might have similar routine health estimates but react very differently to fasting, workouts, poor sleep, or illness. Measuring recovery speed and quality could reveal health information missed by standard annual exams.
The findings were published in PLOS One, expanding on earlier research that appeared in PNAS Nexus in 2024. The researchers hope this approach will eventually enable individuals to utilize their personal long-term health data for more tailored health decisions, rather than following generic lifestyle advice.
The project highlights how dense, continuous health monitoring can uncover subtle changes that routine health checks might miss. Tracking one individual repeatedly provides detailed insights, fostering new questions, measurement techniques, and technologies. It is particularly valuable as an exploratory tool.
However, a major limitation is that the study involved only one person—who also happened to be the lead researcher. The results cannot be generalized to others, as responses to fasting, exercise, and diet can vary widely. It’s also unclear which specific lifestyle changes caused particular effects, as multiple aspects were altered simultaneously.
Caution is also warranted regarding the biological age estimate. A 47-year-old with an apparent biological age of 32 doesn’t mean they have literally reversed 15 years of aging. These estimates depend on the measurement methods and models used, and their predictive validity for long-term health still requires validation.
Furthermore, Ho’s fasting and exercise regimen was quite intensive. Regularly fasting for 20 hours, doing 48-hour fasts, and exercising for 90 minutes every day may not be safe or suitable for everyone—particularly those with certain health conditions, older adults, pregnant women, or individuals with eating disorders. The study should not be viewed as a blueprint for everyone.
Overall, DELTA showcases the potential of highly personalized health tracking rather than proving an anti-aging breakthrough. Its main contribution is illustrating that health is dynamic, and recovery from various challenges can reveal hidden aspects of well-being beyond routine checkups.
Larger, more diverse studies will be necessary to determine if these measurements can reliably predict healthier aging or extend lifespan.
For those interested in wellness, reviewing research on how ultra-processed foods, red meat, and seafood impact longevity can be valuable, along with studies suggesting that olive oil and vitamin D may support healthy aging.