Intermittent Fasting and PT

May 26, 2021

Fasting, or intentional restriction of food intake, has been around for thousand of years. Much of the roots of fasting comes from religious or spiritual ceremonies; today, fasting is often done for the aspects of improving health and longevity, with some still continuing the religious or spiritual purpose. The data on fasting is robust and doctors of physical therapy (DPTs) need to be aware of the benefits, risks, and the how-to of fasting. Let's get started!

Many various forms of fasting exists. Strict or pure fasting includes the abstinence of food altogether. Time restricted fasting or feeding is where a person restricts feeding to a certain number of daytime hours and uses sleep to help create a partial fast. In other words, a person may eat only from 11am to 7pm, while fasting from 7pm to 11am. Some might consider this a form of intermittent fasting, but the true definition of intermittent fasting is where person will consume food ad libitum one day while restricting food the next. Intermittent fasting (IM) has shown much promise in both animal and human studies.

Hoppers and Me

I know a lot about intermittent fasting. I have two peer-reviewed publications on IM, with a focus on longevity and reproduction. Our organism we studied were lubber grasshoppers -- I know, it's a bit funny but they jump and are pretty. Grasshoppers are a great model organism to study because they live on average 80-120 days once in adults stage, they don't need a huge environment, and we can measure lymph (blood), eggs, and other details easily. In summary of our findings, intermittent fasting significantly increases lubber's lifespan (by adding 20-80 more days) and doesn't interfere with egg production. All of these are great findings!


Other studies confirm similar findings in worms, rats, and even some primates. Understanbly, examining humans with IM can be tough, as we live longer and have varied we don't have long-term data on humans yet. But what are the underlying mechanisms for the improvements seen?


To understand the mechanism of why IM helps, it is important to understand some of the theories as to why we age. Many theories exist as to why we age. Some of these include both programmed and error theories such as:

  • Free radical damage
  • Programmed senescence 
  • Immunological factors
  • Cross-linking theory
  • Rate of living (metabolism)
  • Soma vs reproduction trade-off
  • Combination of theories

Intermittent fasting appears to interact with several of these theories of aging. First, reducing food intake can reduce free radical damage from toxic foods like alcohol and highly processed foods. Second, IM may modulate the immune system by stimulating the gut biome and reducing the intake of potentially immune-stimulating substrates in foods (e.g. insulin-like growth factors in cow's milk). Third, IM lowers a person's thermic effect of food and metabolism, thus reducing a person's rate of living. Lastly, IM is a form a calorie restriction, one of the only mechanism scientists have found to extend lifespan.

Less calories = less weight gain = less chronic disease

Human Studies and Implication for PTs

Having such robust data on hoppers and mice is great, but what about humans studies and the impact to physical therapy practice? A well-done systematic review outlines some of the following benefits for humans who undertake IM:

  1. Improved stress response
  2. Lowered cholesterol
  3. Lowered blood pressure
  4. Improved insulin response

Understanbly such benefits could help many of patients in cardiac rehab, neuro physical therapy, and PTs working with diabetes. Some of this data focuses on time-restricted feeding, which many authors consider a form of intermittent fasting. Regardless, reducing food intake for a part or a whole day can confer substantial benefits to our patients.

What about musculoskeletal disorders and IM. Interestingly those who undertake IM during Ramadan, a Muslim fasting holiday, patients with rheumatoid arthritis (RA) and spondyloarthritis (SA) may see significant pain reduction and symptom improvement. The authors argue that IM may "may attenuate the inflammatory state by suppressing pro-inflammatory cytokine expression and reducing the body fat and the circulating levels of leukocytes." As such, PTs working with RA, SA, and other autoimmune patients may want to discuss IM with their patients and possibly seek a registered dietician (RD) referral for help.

Longevity may be a talking point for some authors, but the data is limited in humans at this time. Physical therapists should focus their efforts on educating patients on IM and seeking assistance from trained MDs and RDs as IM does carry some risks.

PTs should be aware that IM is not appropriate:

  • For those with a high caloric need such as in pregnancy or advanced sport
  • For those with history of eating disorders
  • For those feeling weak, tired, extremely hungry, or sick.

In the end, DPTs have advanced training in the neuromusculoskeletal systems; however, understanding IM and implementing a IM program involves careful planning, education, and preparation. Seeking the care of a RD or trained MD (not all MDs are competent in nutrition science let alone IM) is essential!

 If you like what you see here then know there is more in our 3 board-approved continuing education courses on Nutrition specific for Physical Therapists. Enroll today in our new bundled course offering and save 20%, a value of $60!


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Keywords: nutrition, diet, continuing education, online, aging, APTA, PT, physical therapy, learning, physio, fasting, inflammation, lifespan

Disclaimer: The above article is written as opinion piece and does not convey specific legal, medical, and/or practice act advice. 


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