The Buck Institute’s perspective positions energy as a measurable signal of declining health—biology, behavior, and early intervention.
For too long, we’ve viewed the inexorable erosion of our lives—that nagging sense that effort is worth more and recovery is taking longer—as a subjective, undeniable complaint. It’s the classic “I’m getting old” narrative that gets dismissed during a standard exam because the blood panels look “fine.” Dr. Noah Rappaport new word for Buck Institute‘s Healthspan Horizons This will run the script. Rather than being validated by experience, he describes energy as a coherent, quantifiable signal—a biological precursor that exists in our internal systems long before clinical tests enter the red zone (1).
This is not the hunt for a single magical biomarker. Instead, “Energy space” includes all of our integrated living machinery: mitochondrial output, metabolic flexibility, circadian rhythms, and autonomic regulation, all acting in concert. Energy Space: An Early Sign of Declining HealthOne of the first measures of health is slippage, but paradoxically, it remains the least measured (1). We are witnessing a biological drift that precedes overt diseases by years, a subtle fading that marks the real beginning of descent – if we pay enough attention to reading the signal.
Longevity.Technology: If the longevity field has spent the last decade looking for earlier, more subtle signals of decline, then “energy”—long dismissed as irreducibly subjective—may mark a quiet comeback as something highly quantifiable and, most importantly, actionable. The concept of “Energetic activity” refers to fatigue not as an unpleasant symptom, but as an early warning system – a kind of biological whisper that signals a clinical cry – reflecting coordinated changes in mitochondrial functions, metabolic flexibility, autonomic balance, etc. It’s an interesting idea, not least because it creates a constant gap between how aging patients actually experience and how medicine chooses to measure it; after all, few people complain to their doctor about “subclinical mitochondrial dysfunction,” but many will recognize the creeping feeling that effort is worth more and recovery is less rewarding.
The challenge, as always, is in translation—turning this pervasive systems-level signal into something strong enough to guide intervention without collapsing into another layer of well-being abstraction. Wearable models, continuous monitoring, and AI-driven longitudinal models promise to make energy readable as a trajectory rather than a moment, and to shift the focus from population thresholds to personal baselines, but the question remains whether this emerging signal can move beyond lifestyle improvements into the realm of clinically relevant endpoints. If possible, Energy Span may offer a rare convergence—an early and intuitive metric that is both biologically based and socially relevant, not just to how we age, but to how we operate, restore, and ultimately design the systems that sustain or destroy human vitality.
From sign to system signal
Energy, in this framework, is neither a vague sensation nor a diagnostic marker—instead, it is an emergent property of interacting biological systems. Mitochondria sit at the center, controlling ATP production and metabolic signaling, but they function in a broader network that includes hormonal rhythms, inflammatory tone, and neural energy demand. No single measure captures this complexity—instead, Energy Span reflects how well these systems work together in real-world conditions. This systems perspective is consistent with a broader shift in herology from single-pathway explanations to network-level understandings. Decreased energy, reports often loss of ability to adapt, rather than obvious pathology; Dr. Rappaport writes that the pattern that many will recognize before the lab values change is that “effort is more expensive than before, recovery takes longer, concentration decreases during the day.”
Drift, decay and decay
Most importantly, the Energy Span trajectory is not linear. The report presents a dual model of gradual “drift” with sudden “mountain peaks”—episodes such as illness, stress, or hormonal transitions—that accelerate the decline. These turning points can cause permanent changes in mitochondrial function and systemic stability, sometimes with incomplete recovery.
Such a model is consistent with emerging data on aging as a dynamic process shaped by both cumulative wear and discrete insults. It also makes practical sense: if deviations are detected early, there may be a window in which intervention remains viable. Time is important. Earlier still.
Intangible measurement
For decades, the challenge has been measurement. Energy traditionally sits outside the realm of quantification and belongs to subjective reporting. This border is now changing. Advances in wearable technology and continuous monitoring allow tracking energy regulation proxies – heart rate changes as a sign of autonomic balance, glucose dynamics as a reflection of metabolic stability, sleep architecture as a recovery proxy.
We’ve gotten to the point where consumer technology is actually good enough to keep under control. It’s not just about counting steps anymore. Think of it as digital phenotyping – letting your sensors and phone collect the messy, real data of your daily life as a missing piece. When you combine this continuous flow with machine learning, the math changes. You stop chasing individual shots and start watching the trajectory. You can see patterns of your own resilience, subtle declines, and the way you actually recover. It turns the sounds of life into a map you can finally read.
It’s a different paradigm, and it’s less episodic and more continuous… less population-based and more personal. Changes within a person become a signal of interest.
Interference in familiar territory
Despite the design of major reporting systems, the proposed interventions remain largely conventional (1). Exercise, especially when combining endurance and resistance styles, has been shown to be a key factor in mitochondrial health. Sleep regulates circadian and endocrine rhythms by focusing on duration and architecture. Nutrition promotes energy stability through glycemic control and metabolic flexibility. Stress regulation, often indexed by HRV, affects the ability to recover.
There is little innovation in these components individually. Changes in their integration and efforts to connect them depend on measurable and long-term results. Energy is not only something that needs to be “raised”, but something that needs to be trained, sustained and pursued.
Apart from the individual
Rappaport shifts the lens to the structural, where the incompatibility of our work schedules with human physiology becomes undeniable. We don’t just look at individual health choices; we look at the structural erosion of life – a societal design that treats human regeneration as a luxury rather than a luxury. You can’t “biolime” your way out of an environment that is fundamentally designed to drain you. After all, many of us literally live in a state of perpetual social jetlag, where the demands of the hour are at odds with our internal metabolic and hormonal rhythms. When you start measuring energy properly, you realize that this is not a personal and personal struggle – it’s a public health issue. Gathering this information will force changes in how we design our workplaces, as an aging population cannot function with chronic fatigue.
The signal is still taking shape
Whether Energy Span will emerge as a widely accepted metric remains to be seen. Its appeal lies in its intuitiveness—everyone understands energy—and in its potential to bridge molecular biology and life experience. As with most things, its translation into clinical services requires rigorous validation, standardization and, perhaps most difficult, integration into existing health care frameworks.
Now, Energy Span is somewhere between a concept and a tool; promising, plausible, not yet proven. However, the direction is clear. Biology whispers first. The question is whether we are willing to listen.
READ MORE: Healthspan Horizons aims to map healthy aging
Photo by Dr. Noah Rappaport courtesy of the Buck Institute for Aging Research
(1) https://healthspanhorizons.org/energy-span-an-early-signal-of-healthspan-decline/
