You can’t stop aging entirely, but you can measurably slow it down. The science of aging has shifted dramatically in recent years, moving from vague advice about “healthy living” to precise biological targets and ways to measure whether interventions actually work. Some strategies are available right now, others are in early clinical trials, and a few sit on the frontier of gene therapy. Here’s what the evidence actually supports.
Why Your Body Ages
Aging isn’t one process. It’s at least nine overlapping biological breakdowns happening simultaneously in every tissue. Two of the most consequential are epigenetic drift and cellular senescence.
Your DNA doesn’t change much over a lifetime, but the chemical tags that tell your genes when to turn on and off gradually become disordered. Regions of DNA that should stay tightly packed become loose, while others that should be accessible get locked down. The result is that cells slowly lose their identity: a liver cell starts behaving a little less like a liver cell, a skin cell a little less like a skin cell. This epigenetic scrambling accumulates in every tissue and is now measurable with remarkable precision.
Simultaneously, damaged cells that should either repair themselves or die instead enter a zombie-like state called senescence. They stop dividing but refuse to clear out. Worse, they pump out inflammatory signals and tissue-degrading enzymes that damage their neighbors. The number of these senescent cells rises steadily with age and correlates tightly with the visible and invisible decline we associate with getting older.
Cardiorespiratory Fitness Has the Largest Effect
If you could pick one intervention with the strongest evidence for extending lifespan, it’s improving your cardiovascular fitness. A study of over 122,000 adults who underwent treadmill testing found that people with elite fitness had an 80% lower risk of death from all causes compared to those with low fitness. Even moving from below-average to above-average fitness reduced mortality risk by 29%. To put that in context, low fitness carried a higher mortality risk than smoking, diabetes, or heart disease in this dataset.
The key metric is VO2 max, which reflects how efficiently your body uses oxygen during intense exercise. It declines roughly 10% per decade after age 30 if you don’t actively train it. The good news is that it responds to training at any age. High-intensity interval training (short bursts of hard effort followed by recovery) is the most efficient way to improve VO2 max, though any exercise that gets your heart rate elevated consistently will help. Strength training matters too, preserving muscle mass, bone density, and metabolic health, but the mortality data for cardiorespiratory fitness is uniquely strong.
Caloric Restriction: What the Human Data Shows
Eating less has extended lifespan in nearly every organism tested, from yeast to primates. The first rigorous human trial, called CALERIE, put this to the test over two years. Participants assigned to caloric restriction achieved about a 12% reduction in calories on average (not the 25% originally targeted, which gives you a sense of how hard sustained restriction is). Even at that modest level, the results were striking.
Thyroid hormone T3, a marker of metabolic rate, dropped 22% by the end of the study. Tumor necrosis factor alpha, a key inflammatory signal, decreased significantly more than in the control group by 24 months. C-reactive protein (another inflammation marker), triglycerides, total cholesterol, LDL cholesterol, blood pressure, and insulin resistance all improved beyond what the control group experienced. HDL cholesterol (the protective kind) increased. These aren’t longevity data directly, but they represent improvements in nearly every biomarker that predicts lifespan.
The practical takeaway isn’t that you need to count every calorie. Avoiding chronic overeating, maintaining a healthy weight, and occasionally giving your body periods of lower caloric intake (whether through time-restricted eating or other approaches) likely captures much of the benefit without the difficulty of sustained restriction.
Sleep: The 6 to 8 Hour Window
A large meta-analysis of prospective studies found that consistently sleeping between 6 and 8 hours per night is associated with the lowest risk of dying from any cause. Sleeping less than 6 hours or more than 9 hours both carry increased mortality risk, creating a J-shaped curve. Sleep isn’t just passive rest. It’s when your brain clears metabolic waste, your body repairs tissue, and your immune system recalibrates. Chronic sleep deprivation accelerates many of the hallmarks of aging, including inflammation and epigenetic drift.
NAD+ Supplements: Promising but Early
NAD+ is a molecule involved in hundreds of metabolic reactions, including DNA repair and energy production. Its levels decline substantially with age. Supplements called NMN and NR are precursors that your body converts into NAD+. A 12-week trial found that 250 mg per day of NMN (taken as 125 mg twice daily) was safe, well tolerated, and significantly increased NAD+ levels in whole blood. NR has shown similar safety and NAD+-boosting effects in separate trials.
What’s less clear is whether raising NAD+ levels translates to measurably slower aging in humans. The biological rationale is strong: NAD+ fuels a family of proteins called sirtuins that regulate DNA repair and stress responses. But long-term human outcomes data doesn’t exist yet. These supplements are widely available and appear safe at studied doses, but they remain a bet on biological plausibility rather than proven anti-aging therapy.
Clearing Zombie Cells With Senolytics
Senolytic drugs are designed to selectively kill senescent cells, the dysfunctional cells that accumulate with age and drive chronic inflammation. The most studied combination pairs dasatinib (a cancer drug) with quercetin (a plant compound found in onions and apples). In a pilot clinical trial of patients with diabetic kidney disease, this combination reduced systemic inflammation, lowered the number of senescent cells, and decreased immune cell infiltration into fat tissue.
Animal studies have been even more dramatic, showing improvements in physical function, organ health, and sometimes lifespan after clearing senescent cells. But human trials are still in early stages, and these drugs aren’t available as standard anti-aging treatments. Quercetin on its own is sold as a supplement, though its senolytic effects at supplement doses remain unproven.
Cellular Reprogramming: The Frontier
Perhaps the most remarkable development in aging research involves a set of proteins called Yamanaka factors. These four proteins can reprogram adult cells back into stem cells. Full reprogramming creates cancer risk, but partial reprogramming, activating the factors briefly, appears to reverse cellular age without losing cell identity.
In a 2024 study, old mice (equivalent to roughly 80 human years) received gene therapy delivering three of the four Yamanaka factors. Their median remaining lifespan increased by 109% compared to untreated controls. Frailty scores improved. Epigenetic clocks in their liver and heart tissue showed statistically significant age reversal. When the same three factors were applied to skin cells from a 65-year-old human donor, those cells also showed epigenetic markers of age reversal.
This technology is years from human application. Controlling the dose, duration, and delivery of reprogramming factors in a living person without triggering tumor growth is an enormous challenge. But it represents a fundamentally different approach: not slowing aging, but reversing it at the cellular level.
Measuring Your Biological Age
One of the most useful developments for anyone trying to slow aging is the ability to measure it. Epigenetic clocks analyze chemical modifications on your DNA to estimate your biological age, which can differ from your calendar age by years in either direction.
First-generation clocks like Horvath’s clock (accurate to within about 3.6 years on average) and Hannum’s clock (accurate to about 3.9 years) correlate strongly with chronological age. Newer clocks are more clinically useful. PhenoAge combines DNA data with blood biomarkers like C-reactive protein, blood sugar, and kidney function to predict health status and mortality risk. GrimAge integrates smoking status, insulin resistance, and inflammation markers, and is considered the best current predictor of all-cause mortality. The newest AI-based clocks like DeepMAge have pushed accuracy to within about 2.8 years.
These tests are commercially available through several companies. They’re most valuable when taken repeatedly over time, letting you see whether your interventions are actually moving the needle on your biological age rather than just your weight or blood pressure.
What You Can Do Right Now
The interventions with the strongest current evidence form a familiar but powerful list: regular vigorous exercise (particularly the kind that challenges your cardiovascular system), maintaining a healthy body weight without chronic overeating, sleeping 6 to 8 hours consistently, and managing chronic inflammation through diet and movement. These aren’t exotic, but the magnitude of their effects is larger than most people realize. The gap between low and elite fitness alone represents a fivefold difference in mortality risk.
Beyond lifestyle, the landscape is rapidly evolving. NAD+ precursors are accessible now with good safety data but unproven long-term benefits. Senolytics are in clinical trials. Cellular reprogramming has produced startling results in mice. And epigenetic clocks give you a way to track your biological age with increasing precision. The goal of “stopping” aging remains out of reach, but slowing it by a decade or more is increasingly a matter of applying what the science already supports.