What This Functional MD Wants You To Know About Intermittent Fasting & Cancer 

In our society, many believe getting cancer is a predestined fate. An uncontrollable genetic destiny. However, according to nephrologist Jason Fung, M.D., fasting expert and author of The Cancer Code, lifestyle and environmental factors do play a role: When it comes to cancer, "genetics are not the only thing that's important," he explains on this episode of the mindbodygreen podcast. Genetics are key, yes, but there are lifestyle factors at stake that may encourage certain cancers to manifest and grow. 

"If you're going to tip the scales in favor of growth, then you're going to tip the scales in favor of cancer because cancer loves to grow," notes Fung. That's because when your cells constantly grow, without a proper cleanup process to clear out any damaged proteins and organelles, those damaged particles can accumulate in your cells. When this happens, your cells cannot divide and function normally, which can cause cell death1, contribute to age-related diseases, and, yes, have the potential to become cancerous.  

Since your cells grow with more fuel, intermittent fasting "turns off the engine," so to speak, so damaged cells aren't constantly building up. "Once your body recognizes that there are no nutrients coming in, it goes into this repair maintenance mode. It starts to break down all of your old cellular parts and organelles," says Fung (aka, that necessary cleanup process we mentioned above). "It's actually the first step in the rejuvenation process because you've got to get rid of the old stuff first before you can bring in and rebuild that new stuff." 

Of course, much more research is necessary to demonstrate a clear link between the two, but intermittent fasting is a great tool nonetheless (see more of its benefits here). But there are more than a few time-restricted eating plans out there—how long do you need to fast to reap those autophagy-related benefits? 

Here's what Fung suggests: "I think in order to get into autophagy, you have to be up into the 16-plus-hour range." You may need more or less, depending on your exact eating habits and weight, but a 16-hour fast is what he generally recommends. 

However, Fung also encourages an occasional longer fast, if you can handle it. "I think it's always beneficial once in a while to get into a longer state, which is sort of 24 hours plus because then, you're really gonna activate [autophagy]," he says. "You can store sugar in the form of glycogen in your liver, and that will last about 24 hours. [After 24 hours], you can start to break down some of these other proteins you don't need."