Sperling Prostate Center

What’s Up with Intermittent Fasting?

UPDATE: 6/1/2022
Originally published 2/16/2020

Since we posted the blog below, Dr. Valter Longo (Longevity Institute/U of Southern California) and colleague Rozalyn Anderson (Department of Medicine/U of Wisconsin) published a review of biology research on the benefits of dietary restriction.[i] They examined how “key aging genetic pathways are regulated by nutrient levels and composition.” Animal and human studies have demonstrated that during times of food insufficiency, creatures (including us) go into a conservation mode that actually slows aging. Thus, the authors suggest that intermittent or periodic dietary restriction can “generate coordinated responses that are effective against aging and diseases” in ways that are safe for short- and long-term use. Restricting calories has the following measurable effects: greater insulin sensitivity, lower risk for cardiovascular disease, and improved biomarkers of liver health. Also, inflammation is reduced without compromising immune function, which may explain protection against cancer and other aging related diseases. Finally, they discuss the merits of intermittent fasting and various diets. They propose that to optimize lifespan and healthspan, food intake should consist of mid-to-high carbohydrate levels, and low but sufficient protein that is primarily from fish and plants. They caution against a one-size-fits all approach, since individual genetic and metabolic profiles can differ, and urge that those over 65 avoid malnourishment that can lead to frailty. They conclude that such a longevity diet “would be a valuable complement to standard healthcare and that, taken as a preventative measure, it could aid in avoiding morbidity, sustaining health into advanced age.”


Think about this question: would you be willing to put up with hunger pangs and irritability for a couple of weeks if you knew from then on you could live a longer, healthier, and smarter life? Sound unlikely? And yet, the latest scientific evidence suggests that a dietary pattern called intermittent fasting has a big payoff just for putting up with a brief but slightly uncomfortable adjustment period.

Intermittent fasting (IF) is exactly what the term implies: intersperse your normal eating with short periods of eating nothing. While there are many ways of going about this, the two most prevalent methods are:

  1. Confine daily eating to a 6-8 hour window, and don’t eat outside of those hours, or
  2. The 5:2 method in which you eat normally five days of the week, but on two days eat only one moderate-sized meal (500-600 calories).

Many people who choose to practice IF jump in rather abruptly, in which case they may experience hunger pangs and feelings of irritability for 2-4 weeks until their bodies get used to what’s happening. However, there are ways to phase into an IF program (with your doctor’s knowledge and consent) and avoid a discouraging transition. But the question is, why even take on intermittent fasting to begin with?

Benefits of intermittent fasting

The last time I wrote about intermittent fasting I presented the work of Dr. Valter Longo (USC Longevity Institute). This time, I will focus on the work of Mark Mattson PhD, a neuroscientist at the National Institute on aging. For years, he has been studying the benefits of IF at the cellular and molecular levels. In late December 2019, he and associate Rafael de Cabo PhD published an article in the prestigious New England Journal of Medicine titled “The Effects of Intermittent Fasting on Health, Aging and Disease.”[ii]

A major concept behind IF is what Dr. Mattson calls metabolic switching that appears to be an evolutionary adaptation to periods of food scarcity. Metabolism is a pretty broad term, but in this context think of it as the way cells break down nutrient resources and convert them to energy. Metabolic switching happens “…when cells use up their stores of rapidly accessible, sugar-based fuel, and begin converting fat into energy in a slower metabolic process.”[iii]

There is a saying that what doesn’t kill you makes you stronger. While we tend to say this in a tongue-in-cheek way when we’re under stress, it’s actually true if the stressor is essentially good for us. For example, if you do aerobic exercise or weight training, you are “stressing” your body for a good reason—and your body responds favorably with better cardiovascular function or weight management or other benefits. In the same manner, metabolic switching triggers a number of processes that promote health and longevity, and as humans we can trigger metabolic switching by voluntarily “stressing” our cells in a good way, which has beneficial results.

It’s worth highlighting some key benefits from the recent article as well as Mattson’s earlier research:

  • Improved blood sugar regulation
  • Better resistance to stress
  • Reduced inflammation in the body
  • Lowered blood pressure
  • Lowered cholesterol
  • Slower resting heart rate

In addition, “Fasting has been shown to improve biomarkers of disease, reduce oxidative stress and preserve learning and memory functioning…”[iv]

Fasting may also have an indirect effect on prostate cancer. First of all, when consistent, a practice of intermittent fasting can reduce the vulnerability toward obesity and diabetes, both of which are linked with developing cancer. Secondly, fasting helps cell membranes become more sensitive to insulin, helping them metabolize is more efficiently and remove glucose (sugar) from the blood. Better regulation of blood sugar makes it harder for cancer cells to thrive.

However, a 2010 lab animal study on fasting and prostate cancer by Thomas, et al.[v] cautions that mice who fasted two days per week but were allowed to eat freely the other five days tended to overeat on the nonfasting days, thus apparently canceling out any positive effects of IF. In other words, practicing IF two days per week is not a license to go crazy with high-calorie goodies the other five days. This “breaking the fast” has been a concern ever since IF became something of a fad among health-conscious practitioners. “Another concern is that promoters of intermittent fasting will, perhaps unintentionally, encourage extreme behaviour, such as bingeing.”[vi]

That said, Dr. Mattson himself embraces IF in his personal life, and sees it as part of a healthy lifestyle. For yourself, before embarking on IF or any other dietary change, be sure to discuss the merits and possible negative effects on your health with your doctor.

NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.

[i] Longo VD, Anderson RM. Nutrition, longevity and disease: from molecular mechanisms to interventions.” Cell 2022:185(9);1455-1470.
[ii] de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. 2019 Dec 26;381(26):2541-2551.
[iii] “Intermittent fasting: live ‘fast,’ live longer?” WorldPharmaNews, Dec. 27, 2019. http://www.worldpharmanews.com/research/5070-intermittent-fasting-live-fast-live-longer
[iv] Collier, R. Intermittent fasting: the science of going without.” CMAJ. 2013 Jun 11; 185(9): E363–E364.
[v] Thomas JA, Antonelli JZ, Lloyd JC, Masko EM et al. Effect of intermittent fasting on prostate cancer tumor growth in a mouse model. Prostate Cancer Prostatic Dis. 2010 Dec;13(4):350-5.
[vi] Collier, ibid.


About Dr. Dan Sperling

Dan Sperling, MD, DABR, is a board certified radiologist who is globally recognized as a leader in multiparametric MRI for the detection and diagnosis of a range of disease conditions. As Medical Director of the Sperling Prostate Center, Sperling Medical Group and Sperling Neurosurgery Associates, he and his team are on the leading edge of significant change in medical practice. He is the co-author of the new patient book Redefining Prostate Cancer, and is a contributing author on over 25 published studies. For more information, contact the Sperling Prostate Center.

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