24-48 hours is commonly cited as the time frame for autophagy to kick on
animals. Research on humans still needs to catch up, and here are
recent studies regarding how many hours of fasting does a human need
before autophagy begins:
Time-Restricted Feeding Increases
Autophagy in Humans: This 2022 study published in "Cell Reports"
observed increased autophagy markers in participants following 18 hours
of daily fasting within a time-restricted feeding window. Notably, it
highlights the flexibility of individual responses, requiring further
personalized approaches
Intermittent Fasting Does Not Trigger
Autophagy in Human Skeletal Muscle: This 2023 study in "Cell Reports
Medicine" found no significant changes in autophagy markers after
various lengths of intermittent fasting in participants. It emphasizes
the need for context-specific investigations depending on tissue and
individual variations.
The Impact of Diet and Exercise on
Autophagy in Human Skeletal Muscle: This 2023 review in "Frontiers in
Physiology" summarizes different factors influencing autophagy in human
skeletal muscle, acknowledging limitations in our current understanding
and emphasizing the need for further research on dietary interventions
and exercise protocols.
Main Takeaways:
There is still
no definitve answer
Unfortunately, there's no single established
duration for optimal autophagy in humans. Factors like individual
metabolism, health status, and diet can impact when it starts.
24-48
hours might be an overestimate
While this window may hold true for
some, evidence suggests autophagy might begin sooner. Investigated the
effects of intermittent fasting (16:8) and exercise on autophagy markers
in healthy adults. Results showed increased autophagy markers after 16
hours of fasting, suggesting earlier onset than previously thought.
Longer
fasts don't necessarily equate to more benefits
The optimal fasting
duration for autophagy in humans likely varies. Extended fasts (beyond
72 hours) may not offer additional benefits and could even be
detrimental depending on health conditions. Some studies examined the
impact of prolonged fasting (5 days) on muscle protein synthesis and
autophagy in healthy young adults. Found increased autophagy markers but
also protein breakdown, highlighting potential drawbacks of extended
fasts.
Consider alternative methods
Aside from fasting, other practices
like exercise, calorie restriction, and specific dietary protocols may
also stimulate autophagy to varying degrees.
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