So far in this issue, I’ve focused on some of the most cutting-edge advancements for fighting cancer. But some striking new research adds to an already impressive stack of evidence supporting one of the oldest—and simplest—disease-fighting strategies in the book.
I’m talking about fasting.
Now, it might surprise you to hear that calorie restriction could help mobilize the body’s defenses against cancer—especially when conventional advice urges cancer patients to eat whenever and whatever they can.
But as the latest research shows, intermittent fasting (IF) might actually be the most powerful secret weapon in your anti-cancer arsenal.
How fasting keeps breast cancer at bay
Scientists at the University of Southern California recently teamed up with Italian researchers to explore how a fasting-mimicking diet might help treat breast cancer. Their findings were published last year in the journal Nature—and they’re quite eye-opening, to say the least.
For one thing, they found that fasting lowered several key metabolic hormones, including insulin, leptin, and insulin-like growth factor 1 (IGF-1)—which play a role in promoting inflammation and tumor growth.1
In mice, these changes increased the cancer-fighting effects of the hormone-blocking drugs tamoxifen and fulvestrant, while also delaying resistance to them. Which would be exciting all by itself.
But it just so happens that two small clinical trials on women with breast cancer delivered similarly promising results. In these studies, patients receiving estrogen therapy for hormone-receptor positive breast cancer also experienced significant drops in insulin, leptin, and IGF-1 levels with IF.
These changes stuck around for extended periods of time, too. And in mice, at least, translated to long-term anti-cancer activity—shrinking tumors and reversing treatment-resistant tumors.
This is important, because some 80 percent of breast cancers are hormone-receptor positive. Which is exactly what makes drugs like tamoxifen so effective (as I discuss on page 3)—at least, at first. Unfortunately, treatment resistance often rears its ugly head, which undermines any long-term benefit.
But if something as safe and simple as IF could combat this problem? Well, I’d call that a pretty serious breakthrough.
Whether or not the same benefit applies to humans still isn’t fully clear. But the study did show that patients were able to follow monthly cycles of IF for nearly two years without any risk.
So really, what do you have to lose? In my view: Nothing. If anything, published research suggests you have cancer protection—and a whole lot more—to gain…
Reboot an aging immune system
As this new study clearly shows, IF isn’t just a weight-loss strategy. As I’ve explained before, fasting can curb high blood sugar, lower cholesterol and blood pressure, boost cognitive function, and cut inflammation, too.3
And researchers believe fasting may just be the secret to rebooting a weakened immune system. As I shared last year, recent studies show that undergoing several two- to four-day fasting cycles, staggered over the course of six months, can flip a switch that puts your immune system into “turnover” mode.
That’s because, when you’re fasting, your body attempts to conserve energy by cutting the fat—literally and figuratively. It burns through fat and sugar stores for energy, while killing off worn out white blood cells that aren’t pulling their weight anymore.
At the same time, your levels of an enzyme called PKA start to lower. And this eventually sends signals to your body to start producing new, healthy immune cells. (Not to mention how prolonged fasting also lowers levels of IGF-1—the same hormone implicated in tumor growth.)
The end result is a rejuvenated immune system. Which has the potential to work wonders, especially in the fight against cancer.
In fact, one team of scientists found that prolonged fasting reduced levels of circulating PKA—and put the brakes on chemotherapy-related immunosuppression and mortality—in mice.4
And while this doesn’t mean much on its own—mice aren’t real cancer patients, after all—at least one Phase I clinical trial has shown that prolonged fasting in humans—in this case, during the 72 hours prior to chemotherapy—can protect white blood cells and ward off toxicity, as well.
Of course, this is still developing research, focused mainly on mice. So I’m not recommending 72-hour fasts just yet.
But luckily, you don’t need extended fasting periods to get results.
What a difference a day makes
Over the last decade, science has uncovered a long list of impressive benefits from IF. And published clinical studies on humans show there’s plenty to be gained from fasting periods of 36 hours or shorter.
By definition, IF is fasting for 24- to 48-hours on consecutive or alternating days. And it can work in a number of ways.
Usually, it simply involves alternating days of “normal” calorie intake with days of extreme caloric restriction. (Fewer than 600 calories for men, and fewer than 500 calories for women.) But it can also take the form of designated eating “windows” in your day—usually restricted to four to eight hours during which you have your meals. (Like between noon and 6 p.m., which is the schedule I personally follow.)
A newer iteration of the IF strategy relies on a 5:2 approach, where any two days in a single week are fasting days. Just remember, you still need to follow a healthy, balanced diet on non-fasting days to reap the many health benefits. So don’t go crazy reaching for anything in sight just because it’s a caloric intake day.
I fast for a longer period of time at least once a month myself—nothing drastic, just 24 to 36 hours, with plenty of water—in addition to my time-restricted eating windows. I always feel refreshed and energized afterwards. And I find that most people can manage this approach relatively easily.
So if you can do it, you should. Because ultimately, fasting isn’t some fad diet. It’s science-backed way to harness your body’s own natural rhythms to boost longevity and ward off today’s deadliest diseases—including cancer.
- Caffa I, et al. “Fasting-mimicking diet and hormone therapy induce breast cancer regression.” Nature. 2020 Jul;583(7817):620-624.
- Di Tano M, et al. “Synergistic effect of fasting-mimicking diet and vitamin C against KRAS mutated cancers.” Nat Commun. 2020 May 11;11(1):2332.
- Rafael de Cabo R, et al. Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine, 2019; 381 (26): 2541.
- Cheng CW, et al. “Prolonged fasting reduces IGF-1/PKA to promote hematopoietic-stem-cell-based regeneration and reverse immunosuppression.” Cell Stem Cell. 2014 Jun 5;14(6):810-23.