31 January 2020

Intermittent Fasting

Welcome back. I’ve blogged often about food and diet but never about dieting. Though I tread carefully on dieting research studies, I’m more open to research reviews, especially one by researchers affiliated with Johns Hopkins University and the National Institute on Aging of the National Institutes of Health.

It’s hard to bypass a trusted review that concludes intermittent fasting has broad-spectrum benefits for many health conditions, including obesity, diabetes, cardiovascular disease, cancers and neurologic disorders. 

Intermittent fasting (from
What’s Intermittent Fasting?
Intermittent fasting refers to any diet that alternates between periods of restricting calories and eating normally. The three most studied are alternate-day fasting; eating 5 days and fasting 2 days each week; and daily time-restricted feeding (eating only during a limited number of hours, such as 6 or 8, and fasting the remaining hours).

Before You Try It
Adopting these eating patterns is not particularly easy. Before highlighting their benefits, I’d best comment on the “practical considerations” discussed in the review.

You’ll have to contend with lots of food and related advertising.

You may experience hunger, irritability and problems concentrating when fasting, side effects that usually disappear within a month.

It is important that physicians provide adequate information, ongoing communication, support and positive reinforcement; however, you might have difficulty finding a physician trained in intermittent-fasting interventions. A dietitian or nutritionist should also be consulted for counseling and education.

Intermittent Fasting Effects
I refer you to the researchers’ report for the referenced studies and nitty gritty of how our bodies respond to intermittent fasting, but I offer the following summary.

Most if not all organ systems respond in ways that enable our bodies to tolerate or overcome the challenge and restore homeostasis. Repeated fasting causes cells to engage in a coordinated adaptive stress response that leads to increased expression of antioxidant defenses, DNA repair, protein quality control, suppressed inflammation and other processes that generally improve cells (mitochondrial biogenesis, autophagy). 

Benefits of intermittent fasting by Johns Hopkins Medicine (graphic modified from www.hopkinsmedicine.org/news/newsroom/news-releases/intermittent-fasting-live-fast-live-longer).

Health and Aging--Years of research with animals has concluded that reduced food intake increases lifespan. In humans, intermittent fasting ameliorates obesity, insulin resistance, dyslipidemia, hypertension and inflammation. The health benefits seem to exceed those attributed to reduced caloric intake.

Physical and Cognitive Effects--Studies have shown that intermittent fasting improves physical function in animals and humans. Young men lost fat while maintaining muscle mass during two months of resistance training. Mice have better running endurance, balance and coordination.

Humans have shown improved verbal and working memory, executive function and global cognition. Animal cognition has been enhanced in multiple domains--spatial memory, associative memory, working memory.

Clinical Applications--In cancer research, numerous animal studies have shown reduced occurrence of spontaneous tumors during normal aging, suppressed growth of many types of induced tumors and increased sensitivity to chemotherapy and irradiation. Case studies involving humans with glioblastoma suggest suppressed tumor growth and extended survival.

Similarly, studies in preclinical animal models and humans have shown promise with obesity, diabetes and cardiovascular disease. There is strong preclinical animal model evidence of delayed onset and progression of Alzheimer’s disease and Parkinson’s disease. Promising results have also been found with asthma in obese patients and in animal and human studies of multiple sclerosis, arthritis and surgical and ischemic tissue injury.

Wrap Up
Animal models show intermittent fasting improves health over the lifespan, yet clinical studies, while positive, have been short-term, generally months. Can people maintain intermittent fasting for years and potentially accrue the benefits seen in animal models?

On the other hand, further research could lead to pharmacologic therapies that mimic the effects of intermittent fasting. Maybe we won’t have to make substantial changes to our feeding habits.

Once again, stay tuned. And thanks for stopping by.

Study of intermittent fasting in New England Journal of Medicine: www.nejm.org/doi/full/10.1056/NEJMra1905136
Article on study on EurekAlert! website: www.eurekalert.org/pub_releases/2019-12/jhm-ifl121819.php

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