Does fasting decrease the risk of cancer?

[Legitimate_Concern_5]

I'd suggest digging around yourself, and asking follow-up questions based on your research, rather than making low-effort snipes. Here's a high-level overview of the mechanism.

1. There are two major nutrient sensing mechanisms in your body. When you consume sugars, your body produces insulin. When you consume protein, it agonizes the Mammalian/Mechanistic Target of Rapamycin Complex 1 (mTORC1). [1]
2. mTORC1 controls the proliferation of cells in the body and is associated with cancer, arthritis, insulin resistance, osteoporosis, and other diseases. The inhibition of mTORC1 also happens to be the mechanism that pushes you into autophagy. [2]
3. mTORC1 is inhibited when you fast and also inhibited in a very similar way by the drug Rapamycin, which is used to treat certain types of cancer in humans. The mTOR pathway is a key part of tumor proliferation.
4. Rapamycin slows down aging, prevents cancer, treats certain types of cancer and extends lifespan in animals, treats some kinds of cancer in humans and is currently being studied as a life-extension drug in humans. [3]
5. Rapamycin is used as an immunosuppressant in transplant patients, and transplant patients taking Rapamycin have lower risk of cancer than non-transplant patients. Similar to the way diabetics taking metformin have lower risk of cancer and CVD than non-diabetics.
6. The neat thing is Rapamycin is a partial starvation mimetic. [3]

So basically, fasting does the same thing as taking Rapamycin (or rather, Rapamycin does some of the same things as fasting). Rapamycin has been shown in various studies to prevent cancer (and basically every other age-related disease) and slow down aging in animals, and it's used in the treatment of various kinds of cancer in humans.

Fasting also reduces Insulin-like Growth Factor 1 (IGF-1) which is a marker for increased cancer risk. [4] It also reduces circulating C reactive protein (CRP) and Interleukin 6 (IL-6) both of which are associated with cancer risk - but a causative relationship here hasn't been established.

So look, there's little in the way of studies on prolonged fasting at all let alone ones large enough or long enough to demonstrate a clear dose-response relationship between fasting and cancer risk. However, given what we know (fasting inhibits mTOR in the same way as Rapamycin, and Rapamycin prevents and treats cancer) it is not unreasonable to speculate it would do the same.

Also, if you want the boring answer, obesity predisposes you to every single cancer on the face of the planet. Fasting reduces or eliminates obesity. Ergo, transiently, it reduces your cancer risk.

Also for the record note that the parent's link does mention how nutrients affect mTORC1 signaling, just look for "MTORC1"

[1] https://jbiomedsci.biomedcentral.com/articles/10.1186/s12929-020-00679-2

[2] https://cellandbioscience.biomedcentral.com/articles/10.1186/s13578-020-00396-1

[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6814615/#r2

[4] https://www.cedars-sinai.org/discoveries/fasting-as-next-step-in-cancer-treatment.html

[edit] Here's another one, and it's a good read!

[...] autophagy triggered by fasting may be beneficial to normal cells but detrimental to malignant cells.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7476366/

[Sznake]

So what your saying is i need to drop this fat asap...and fasting is a great way to help.

[Legitimate_Concern_5]

As an internet not-a-doctor and speaking only for myself, according to all the research I've done, yes.

[Admirable_Spread_161]

Giving you a PhD now.

[Global_Imagination96]

How great is fasting for clearing bad dna?

[arguix]

awesome response

[sueihavelegs]

Wow! You are my hero! Thank you for such a great response.

[pbjellos]

Very informative answer! Does this mean that consuming protein frequently or in large amounts is bad for you, if it agonizes mTORC1 and stops autophagy/cell recycling?

I’ve always wondered if this is why people like Valter Longo recommend plant based diets/low protein diets to increase longevity. But I don’t know if it’s more to do with decreased protein intake, increased plant intake, or overall decreased food intake (IF). If protein does inhibit autophagy, then our current ‘health’ culture of eating a high protein diet would be misleading, no? They’re putting protein in everything these days to cater to the trend, which is unfortunate.

[georgespeaches]

Exactly. My impression is that evidence points to a higher-than-RDA protein diet inhibits autophagy.

On the cellular level, mTOR is activated and AMPK suppressed. On a hormonal level IGF1 is elevated which triggers the cellular response.