Your cells build new mitochondria (the power plants inside your cells) when they're repeatedly asked for more energy than they can easily supply. The most proven trigger by far is regular aerobic exercise. Research suggests more total training time mainly builds more mitochondria, while harder efforts mainly make each one work better, so a mix of both works best. Cold exposure builds mitochondria in brown fat, a special heat-making fat. Pills that promise to "boost mitochondria" haven't been shown to build them in healthy people.
- SymptomLess stamina, tire faster
- Before thatMuscles can't produce energy fast enough
- Before thatFewer mitochondria, and each works less well
- RootNot enough signals telling cells to build more
Your cells can build new power plants
Mitochondria aren't fixed. Your cells can make new ones in a process called mitochondrial biogenesis, literally "the birth of new mitochondria". It's controlled by a master switch, a protein (one of the cell's molecular machines) called PGC-1α, that turns on the whole construction program when the cell senses it needs more energy capacity.
What flips that switch? Mostly one thing: being asked, again and again, to produce more energy than is comfortable. That's why the most powerful tool here is free.
Volume builds more. Intensity builds better.
This is the part most "boost your mitochondria" articles miss. A large review of human training studies found that the two main training dials do different jobs:[1]
- Total training volume (how many minutes you train per week) mainly increases how many mitochondria you have.
- Intensity (how hard you push) mainly improves how well each one works.
Think of it like a factory. Hours of steady work convince management to build more production lines. Occasional rush orders force each line to run faster and smarter. You want both.
And it works at any age. In a study comparing active and inactive people, older adults who trained regularly had muscle mitochondria that produced energy as well as those of active young adults.[2] In another trial, previously inactive older adults raised their mitochondrial capacity after 12 weeks of interval training.[3]
Only one special type of cardio builds mitochondria.
Both longer steady sessions and harder intervals build mitochondria, in different ways. The best plan uses both.
Use it or lose it, fast
There's a flip side. In one study, when people sharply cut back their training, the gains in mitochondria they'd built faded within weeks.[6] Your body doesn't keep expensive power plants it isn't using. That's why steady, year-round habits matter more than an intense six-week program followed by a long break.
Other signals, ranked
Cold exposure
B · Small human studiesTen days of spending six hours a day in a cool room (about 15 to 16°C, 59 to 61°F) increased activity in people's brown fat, a special type of fat packed with mitochondria that burns energy to make heat.[4] But it didn't change mitochondria in muscle. Good for brown fat; not a substitute for training.
Fasting and calorie restriction
C · Mostly animalLow energy activates the cell's fuel gauge, a protein called AMPK, which helps trigger both building and recycling of mitochondria. Convincing in animals; thin in humans.
"Mitochondria booster" supplements
Weak for this purposeNAD⁺ boosters raised NAD⁺ in older men but didn't change how well their muscle mitochondria made energy.[5] Urolithin A, a compound gut bacteria make from pomegranates and walnuts, helps recycle old mitochondria rather than build new ones (see does urolithin A work?).
A simple weekly plan that does both jobs
Not medical advice, just the pattern the research points to. If you're new to exercise or have a health condition, check with your doctor first.
- Volume: 150 minutes or more a week of moderate effort, like brisk walking, cycling or swimming, where you can talk but not sing. This is also the World Health Organization's baseline recommendation for adults.
- Intensity: once or twice a week, add a few short harder efforts, for example 4 to 6 rounds of 1 minute fast, 2 minutes easy.
- Consistency: keep it going year-round. The signal only works if it keeps coming.
The bottom line
You can't buy new mitochondria in a bottle, but you can build them at any age. Steady minutes build more of them; harder efforts make them better. Keep sending both signals, and your cells keep the power plants running. For why this matters so much for daily energy, read why you're always tired after 40.
Frequently asked questions
How long does it take to build new mitochondria?
Measurable increases in muscle mitochondria typically show up after a few weeks of consistent training, with bigger changes over 6 to 12 weeks. They also fade within weeks if you stop, so consistency beats intensity bursts.
Can supplements increase mitochondria?
Not convincingly in healthy people. NAD⁺ boosters raise NAD⁺ levels but didn't change mitochondrial energy production in a trial in older men. Urolithin A helps clear old mitochondria, with modest effects in small trials. Exercise remains far ahead.
Does fasting increase mitochondria?
In animals, energy stress like fasting activates the same switches that trigger mitochondrial building and recycling. Direct evidence in humans is limited, so we grade it C.
Is walking enough to build mitochondria?
Brisk walking counts, especially if you're starting from little activity. As you get fitter, longer sessions and some harder intervals keep sending a strong signal.
Sources
- Granata C, Jamnick NA, Bishop DJ. Training-induced changes in mitochondrial content and respiratory function in human skeletal muscle. Sports Medicine, 2018.
- Lanza IR, et al. Endurance exercise as a countermeasure for aging. Diabetes, 2008.
- Robinson MM, et al. Enhanced protein translation underlies improved metabolic and physical adaptations to different exercise training modes in young and old humans. Cell Metabolism, 2017.
- van der Lans AA, et al. Cold acclimation recruits human brown fat and increases nonshivering thermogenesis. Journal of Clinical Investigation, 2013.
- Elhassan YS, et al. Nicotinamide riboside augments the aged human skeletal muscle NAD+ metabolome and induces transcriptomic and anti-inflammatory signatures. Cell Reports, 2019.
- Granata C, et al. Mitochondrial adaptations to high-volume exercise training are rapidly reversed after a reduction in training volume in human skeletal muscle. FASEB Journal, 2016.