Quick answer: Autophagy, meaning “self-eating,” is how cells break down and recycle damaged parts. Fasting may increase autophagy by activating the energy sensor AMPK, turning down the growth signal mTOR and switching on FOXO genes. Autophagy helps clear damaged proteins, calms inflammation and supports immunity and brain health. Most evidence comes from cell and animal studies.
Key takeaways
Autophagy is the natural process cells use to break down and recycle damaged proteins and worn-out parts.
When food is scarce, the body shifts toward fat for fuel, and that energy shift is one of the signals thought to switch autophagy on.
Autophagy tends to decline with age, and activity, sleep and sensible eating patterns may help support it, although much of the research is still in animals.
What is autophagy?
A natural process where cells break down and recycle damaged proteins and organelles.
How fasting triggers autophagy
Much of this research comes from animal studies, and results in people vary.
Energy conservation
With less food, the body shifts from glucose to fat for fuel.
AMPK activation
AMPK senses low energy and switches on autophagy.
mTOR inhibition
mTOR drives growth when nutrients are plentiful; fasting turns it down, allowing autophagy.
FOXO transcription factors
Fasting activates FOXO genes that regulate autophagy and stress resistance.
Possible benefits of autophagy
Possible benefits include clearing damaged proteins and organelles, lower inflammation and oxidative stress, helping the immune system clear some microbes, and supporting brain cells.
Autophagy and healthy aging
Autophagy declines with age, allowing damaged proteins and mitochondria to build up. Supporting it through activity, sleep and sensible eating patterns is a promising healthy-aging strategy. For the longevity angle, see autophagy and longevity; for daily habits, see autophagy mastery.
What the research shows
Most autophagy research comes from cells and animals. Only a few small human studies have looked for signs of autophagy during fasting.
Autophagy markers in people (Jamshed 2019, randomized crossover study). 11 adults with overweight ate between 8 a.m. and 2 p.m. for 4 days and between 8 a.m. and 8 p.m. for 4 days. The early window lowered average 24-hour glucose by 4 mg/dL and, in morning blood samples, raised ketones and the activity of the autophagy-related gene LC3A and the gene SIRT1. A key limitation is that gene activity in blood cells is only an indirect sign of autophagy; the study did not measure autophagy in tissues, and it lasted only 4 days in 11 people.
Early eating window without weight loss (Sutton 2018, controlled crossover feeding trial). 8 men with prediabetes ate all their food within 6 hours, finishing dinner before 3 p.m., for 5 weeks, and then ate across a 12-hour window for 5 weeks. Food was supplied so their weight stayed the same. The early window improved insulin sensitivity, blood pressure and markers of oxidative stress. The obvious limitation is size: only 8 men took part, and an eating window that ends at 3 p.m. is hard for most people to keep.
Strength of the evidence: Human evidence is early and indirect, based on gene activity in blood cells and short studies with fewer than a dozen people.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have diabetes, take blood sugar or blood pressure medication, or have a chronic condition, or if you are pregnant, breastfeeding, underweight, or have a history of disordered eating. The same is true if fasting leaves you dizzy, shaky or exhausted, or if you want a fasting approach tailored to your health goals.
See a medical provider promptly for fainting, confusion, chest pain, a racing heartbeat, or very low blood sugar symptoms such as shaking, sweating and confusion.
Want a fasting plan that fits your health?
A free 15-minute consultation with Dr. Kneessi. No cost, no obligation. In-office in Odenton, MD or by telehealth.
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
Is a fasting window a reasonable way for me to support cellular recycling, or are other habits a better fit?
How long a fasting window would be reasonable for me to try?
Are there ways to support autophagy without long fasts?
Would fasting be safe for me, given my health history?
Frequently asked questions
How long do you have to fast for autophagy?
It isn’t known precisely in humans; it likely varies by person and tissue.
Does exercise trigger autophagy?
Yes, exercise also stimulates autophagy.
Is autophagy anti-aging?
It is linked to healthy aging in research, but individual results are uncertain.
Can I measure autophagy?
Not with routine tests.
Sources
- Mizushima N, Komatsu M. Autophagy: renovation of cells and tissues. Cell 2011. PMID: 22078875. https://pubmed.ncbi.nlm.nih.gov/22078875/
- Kim J, et al. AMPK and mTOR regulate autophagy through direct phosphorylation of Ulk1. Nat Cell Biol 2011. PMID: 21258367. https://pmc.ncbi.nlm.nih.gov/articles/PMC3987946/
- Mammucari C, et al. FoxO3 controls autophagy in skeletal muscle in vivo. Cell Metab 2007. PMID: 18054315. https://pubmed.ncbi.nlm.nih.gov/18054315/
- Levine B, Kroemer G. Autophagy in the pathogenesis of disease. Cell 2008. PMID: 18191218. https://pmc.ncbi.nlm.nih.gov/articles/PMC2696814/
- Rubinsztein DC, Mariño G, Kroemer G. Autophagy and aging. Cell 2011. PMID: 21884931. https://pubmed.ncbi.nlm.nih.gov/21884931/
- National Institute on Aging: Research on intermittent fasting shows health benefits
- National Institute on Aging: Calorie restriction and fasting diets: What do we know?
- Jamshed H, et al. Early Time-Restricted Feeding Improves 24-Hour Glucose Levels and Affects Markers of the Circadian Clock, Aging, and Autophagy in Humans. Nutrients 2019. PMID: 31151228. https://pubmed.ncbi.nlm.nih.gov/31151228/
- Sutton EF, et al. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab 2018. PMID: 29754952. https://pubmed.ncbi.nlm.nih.gov/29754952/
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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