What is autophagy and can I activate it myself?
You can promote autophagy yourself through fasting or temporarily eating significantly less, and probably through exercise as well. Do not overdo it: extreme caloric restriction can actually damage the cell.
Autophagy is your cells' internal clean-up system. Damaged components, misfolded proteins and even invading pathogens are packaged, broken down and recycled. Without this system, cellular waste accumulates, contributing to ageing and disease. As you get older, the activity of this system declines, and that goes hand in hand with a greater build-up of damaged components inside your cells.
The most powerful way to activate autophagy is simply to eat less, or to stop eating temporarily. Both traditional fasting and low-calorie fasting periods switch on autophagy in a large number of organs and tissues. A randomised study in 46 healthy adults showed that seven days at 850 kilocalories per day, regardless of whether protein intake was low or high, activated autophagy at the cellular level and also lowered blood sugar. Caloric restriction itself is therefore the driving force, not the specific distribution of nutrients.
Intermittent fasting probably works because it alternately puts the cell into a clean-up mode and a growth mode. During the fasting phase, the activity of mTOR, a protein that normally suppresses autophagy, falls. During the eating phase, the cell stores energy and grows instead. That alternation may offer greater benefits than continuous calorie reduction, although the evidence in humans is still limited.
Exercise does something similar: it inhibits that same mTOR and activates autophagy in multiple tissues. The evidence for this is less extensive than that for fasting, but the signalling pathways overlap strongly. An eating pattern with two to three meals per day and an emphasis on eating earlier in the day is also associated with more autophagy and less inflammation, but this is largely based on observational research and is less well supported.
An important caveat: more is not automatically better. Extreme and prolonged caloric restriction can lead to excessive autophagy, and that can damage or even kill cells. In practical terms, mild and well-defined fasting periods are the safest way to promote autophagy, rather than extreme diets. Anyone who wants to experiment seriously with fasting would be wise to discuss this with a doctor, especially if underlying health conditions are present.
Evidence based on multiple reviews and one randomised study in 46 people (PMID 40816210). Mechanistic evidence for mTOR inhibition and lifespan extension comes largely from animal and cell studies. The evidence for exercise and eating patterns in humans is less extensive.
Can you measure autophagy in your body?
There is no reliable, simple method yet for measuring autophagy in your body. Scientists use combinations of indirect markers, but these are for now confined to research laboratories.
What does autophagy do for ageing and disease?
Autophagy is a genuine part of the ageing process and plays a role in many age-related diseases, but the translation into proven human interventions has not yet been made. What you can do now: exercising regularly, sleeping enough and fasting occasionally are the best-supported ways to keep this cellular system active.
What is apoptosis and why is it beneficial for cells to clean themselves up?
Apoptosis is an indispensable clean-up mechanism that keeps your body healthy, but balance is everything: too little increases the risk of cancer, too much damages the brain and other vulnerable tissue.
Why do cells lose their ability to repair themselves over time?
Cells lose their repair capacity through a combination of declining energy stores, impaired DNA repair and the accumulation of 'burned-out' cells that secrete inflammatory substances. These are well-supported mechanisms, although it is still too early to act on them through supplements or therapies.
Does exercise activate autophagy?
Exercise activates autophagy in muscle cells through well-described mechanisms, but most of the evidence comes from animal and laboratory research. In practice: regular, moderate exercise appears most beneficial; extremely excessive loading could actually dysregulate the system.
How many hours of fasting are needed to activate autophagy?
There is no proven hourly threshold for activating autophagy in humans. If you use this as a reason for a fasting pattern, be aware that the mechanistic idea is plausible, but the practical threshold in humans has not yet been established.