Autophagy

The cell's recycling process, in which damaged proteins and organelles are packaged and broken down for reuse, upregulated by fasting and exercise.

What it is

Autophagy is how a cell disposes of its own damaged parts. A membrane forms around the target, delivers it to the lysosome, and the contents are broken into amino acids and fats that the cell reuses. Selective forms handle specific cargo, including mitophagy for worn out mitochondria.

It runs continuously at a baseline level and increases when nutrients are scarce. Genetic disruption of autophagy shortens lifespan in yeast, worms, flies and mice, which is why it is treated as a core mechanism of aging rather than a wellness idea.

What raises it

Nutrient scarcity is the strongest known signal, sensed largely through mTOR inhibition and AMPK activation. Exercise raises it in muscle and other tissues. Rapamycin raises it pharmacologically, which is part of why it extends lifespan in mice.

That much is solid. The step people skip is quantification. In humans, autophagy cannot currently be measured directly outside of a tissue biopsy with specialized assays, so no fasting protocol has been shown to hit a particular level of autophagy in a living person.

How to read fasting claims

Statements like autophagy switches on at 16 hours are extrapolations, usually from rodent work where the metabolic rate and fasting timeline are quite different from ours. The direction is right and the specific hour is invented.

There is also a limit to the more is better framing. Autophagy is a maintenance process, not a treatment, and chronic aggressive fasting in someone already lean and training hard trades muscle for a mechanism nobody is measuring.

Nothing Baseline dispenses targets autophagy directly, and there is no validated way to measure autophagy in a living person outside a research biopsy.

References

  1. Mizushima N, Komatsu M. Autophagy: renovation of cells and tissues. Cell. 2011.
  2. Klionsky DJ, et al. Autophagy in major human diseases. EMBO J. 2021.
  3. Escobar KA, et al. Autophagy and aging: maintaining the proteome through exercise and caloric restriction. Aging Cell. 2019.