Autophagy
A cellular "clean-up" process in which cells break down and recycle their damaged components, triggered notably by fasting and exercise, and key to healthy ageing.
The term comes from the Greek “auto” (self) and “phagein” (to eat): literally “eating oneself”. It is the cells’ internal recycling system. They enclose waste (defective proteins, worn-out mitochondria, aggregates) in membrane “bags” (autophagosomes) and then digest them to reuse the materials.
The original angle (the Nobel Prize and the “rubbish bags”): the importance of autophagy earned Yoshinori Ohsumi the 2016 Nobel Prize in Medicine. A recent discovery (Institut Pasteur, 2024) even visualised how “starved” cells build these bowl-shaped rubbish bags to collect waste, paving the way for drugs that would activate autophagy.
Triggers of autophagy:
- Fasting: after ~12-16 hours without eating, autophagy intensifies (the body, deprived of outside nutrients, recycles its own)
- Exercise: stimulates muscle autophagy
- Calorie restriction
- Certain compounds (resveratrol, spermidine, coffee)
An honest scientific caveat: the mechanisms are well documented in animals, but in humans the evidence, though promising, remains limited. The fasting threshold needed in humans is not precisely known (the famous “16 hours” is extrapolated). Beware of excessive enthusiasm: autophagy is not a “magic elixir”.
The link with health and ageing: autophagy declines with age. Stimulating it is being studied against neurodegenerative diseases (it breaks down the toxic aggregates around neurons in Alzheimer’s and Parkinson’s), diabetes and ageing. It also protects against cancer (by eliminating defective cells) while sparing healthy cells.
Key point: autophagy is opposed by a constantly “fed” state (permanent snacking, chronically high insulin which inhibits it). Alternating fed and fasted periods is the rhythm that allows it.