Zone 2 Training: The Evidence for Longevity and Health
Autophagy tracks your training alongside cold, breathing, fasting and sauna, so the whole practice adds up. Free on iPhone.
Of the five practices, exercise has the deepest evidence base of all, and zone 2, the easy aerobic end of it, has become the fashionable way to talk about training for a long life. The fashion is mostly justified, but not for the reason people usually give. Here is the honest read.
The real reason it matters
Strip away the mitochondrial jargon and the case for aerobic training rests on one of the most robust findings in all of health research: cardiorespiratory fitness, measured as VO2 max, is the strongest modifiable predictor of how long you live. A large 2018 study of over 120,000 people found that low fitness carried a greater mortality risk than smoking, diabetes or high blood pressure, and that there was no observed ceiling, fitter was better all the way up (Mandsager et al., JAMA Network Open, 2018). Moving from the bottom quartile of fitness to merely below average roughly halved ten-year mortality risk.
That is the point of zone 2. It is the most sustainable way to build and defend the aerobic base that underpins VO2 max.
What zone 2 does at the cellular level
Zone 2 is steady work at a conversational pace, easy enough to talk but not sing. Trained consistently, it increases the number and function of your mitochondria, builds capillaries that deliver more oxygen to muscle, improves your ability to burn fat for fuel, and raises insulin sensitivity. And like all exercise, it is a potent trigger for autophagy, the cellular clean-up process that sits at the heart of this whole approach. Muscle is one of the tissues where exercise-induced autophagy has been most clearly shown.
The honest caveats
Here is where I part company with some of the louder zone 2 advocacy. A 2025 Sports Medicine review argued that zone 2 alone, at the doses most people actually do, is not the optimal way to raise VO2 max or mitochondrial capacity in anyone who is not already a competitive endurance athlete. The strong, consistent evidence is that VO2 max predicts mortality; the claim that zone 2 specifically is the best route there is weaker. In practice that means: build an easy aerobic base with zone 2, but do not neglect some harder, higher-intensity efforts that push VO2 max directly, and keep lifting weights. The base matters, but it is not the whole building.
How to train it
A reasonable structure is three to four zone 2 sessions a week of 30 to 60 minutes, kept genuinely easy, plus one or two harder sessions and two strength sessions. The discipline of zone 2 is going slow enough, which is harder than it sounds, because ego pushes the pace up. If you can still talk in full sentences, you are doing it right.
Log your sessions and see your training stack with the other four practices.
Where exercise fits
Exercise is one of five levers, alongside cold, breathing, fasting and sauna. For the deeper cellular version, I wrote a longer piece on exercise and autophagy, and a hub on how to trigger autophagy that ties all five together.
Frequently asked questions
What is zone 2 training?
Zone 2 is steady aerobic exercise at an easy, conversational pace, roughly 60 to 70 per cent of your maximum heart rate. The test is simple: you should be able to hold a conversation but not sing. It is meant to feel almost too easy.
Why is zone 2 good for longevity?
Zone 2 builds aerobic fitness, and aerobic fitness measured as VO2 max is the single strongest modifiable predictor of all-cause mortality. A large 2018 study found low fitness carried a bigger risk than smoking or diabetes. Zone 2 also improves mitochondrial density, fat burning and insulin sensitivity.
How much zone 2 should I do?
A common target is three to four sessions a week of 30 to 60 minutes. The exact dose matters less than doing it consistently, keeping it genuinely easy, and pairing it with some harder efforts and strength work.
Is zone 2 enough on its own?
Probably not, if your goal is peak fitness. Recent reviews argue that zone 2 alone, at the doses most people do, is not the fastest way to raise VO2 max. The best approach combines an easy aerobic base with some higher-intensity work and resistance training.
Does exercise trigger autophagy?
Yes. Exercise is one of the most reliable triggers of autophagy, your cells’ clean-up and recycling process, with good human and animal evidence. Both steady aerobic work and harder efforts contribute.