Fasting before exercising – Top 3 takeaways from Dr. Rhonda Patrick

Written By Katherine O

Fasting before exercise and the effect on endurance, aerobic, and strength training 

An interview with fasting expert, Dr. Rhonda Patrick. 


The question of when the optimal time is to fast and eat for athletes comes up frequently on our calls. In this short video Rhonda Patrick summarizes what we know on this topic and when it is best to work out in a fed vs. fasted state (hint: it depends on the type and duration of the exercise). 

The best answer for you, get clear on the following:

  1. What is your goal? Are you trying to build muscle? Increase endurance? Raise your heartrate? 
  2. What type of exercise are you looking to do? Run a marathon? Weight train? HIIT?
  3. At what point in the fast are you looking at exercising? Within a few hours of your last meal? After 16+ hrs of fasting? Or are you willing to be flexible on this? 

To summarize the findings:

  • For long-duration athletes (doing 60+ min runs, or very long swims) or running to the point of complete exhaustion — if you are completing these types of workouts you will likely benefit from eating prior to beginning your workout.
  • For weight training or high-intensity moderate duration workouts, you get robust improvement in your glucose sensitivity and mitochondrial adaptations to using fatty acids for fuel as well as increased activity in genes that are tied to fatty acid metabolism if you workout in a fasted state.
  • If you’re looking to put on muscle, there used to be a belief that you had to have protein and amino acids almost immediately after a workout to maximize the growth, it is now believed that this window is likely much longer than we used to believe.
    • However, given that we don’t store protein well, if you are looking to build more muscle and are exercising toward the end of a fast (~16hrs+) it may benefit your body to have protein pretty quickly after completing that workout, though that will turn on mTor, which turns off autophagy. So, going back to your goals… you need to know what your primary objective with this fast is so you can choose the correct protocol for you

An additional consideration not mentioned in her video, there is a lot of research to suggest that Human Growth Hormone (HGH) increases 3-fold with longer duration fasts (24-72 hrs) in healthy lean patients. Unfortunately, this benefit seems to be muted initially in obese individuals, where hormone physiology tends to be more generally dis-regulated.  HGH is a key player in building strong bones and muscles. It is the same hormone that fuels childhood growth and influences our height. 

Synthetic HGH is quite controversial and has many negative consequences (think of the stereotypical body builder side-effects), but naturally increasing HGH does not appear to come with those problems. Thus fasting can be a great way to increase HGH without creating negative unintended consequences. 

For those not familiar with Dr. Rhonda Patrick, She did her graduate research at St. Jude Children’s Research Hospital where she investigated the link between mitochondrial metabolism, apoptosis, and cancer.  Her groundbreaking work discovered that a protein that is critical for cell survival has two distinct mitochondrial localizations with disparate functions, linking its anti-apoptotic role to a previously unrecognized role in mitochondrial respiration and maintenance of mitochondrial structure. Her dissertation findings were published in the 2012 issue of Nature Cell Biology.

Dr. Patrick trained as a postdoctoral fellow at Children’s Hospital Oakland Research Institute with Dr. Bruce Ames.  She investigated the effects of micronutrient (vitamins and minerals) inadequacies on metabolism, inflammation, DNA damage, and aging and whether supplementation can reverse the damage. In addition, she also investigated the role of vitamin D in brain function, behavior, and other physiological functions. In February of 2014 she published a paper in FASEB on how vitamin D regulates serotonin synthesis and how this relates to autism.

Dr. Patrick has also done research on aging at the Salk Institute for Biological Sciences. At the Salk she investigated what role insulin signaling played in protein misfolding, which is commonly found in neurodegenerative diseases.

She frequently engages the public on topics including the role micronutrient deficiencies play in diseases of aging, the role of genetics in determining the effects of nutrients on a person’s health status, benefits of exposing the body to hormetic stressors, such as through exercise, fasting, sauna use or heat stress, or various forms of cold exposure, and the importance of mindfulness, stress reduction, and sleep.  It is Dr. Patrick’s goal to challenge the status quo and encourage the wider public to think about health and longevity using a proactive, preventative approach.” – This is quoted from the bio on Dr. Patrick’s website.


For those who love the science, here’s a few additional links I think you’ll enjoy: 


  • Also, here are a few other fasting resources you may enjoy:
    • The Fasting CureSinclair, author and enthusiastic faster, shared his knowledge on the subject both in Cosmopolitan Magazine (very different than the modern Cosmo magazine) and in this book, The Fasting Cure
    • Why We Get Fat and What We Can Do About It – What’s making us fat? And how can we change? Building upon his critical work in Good Calories, Bad Calories and presenting fresh evidence for his claim, bestselling author Gary Taubes revisits these urgent questions.
    • Some of Dr. Jason Fung and Dr. Megan Ramos’ other books: The Obesity Code,The Diabetes Code, and The Cancer Code

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1 Comment

  1. Tina O

    I like the Rhonda Patrick one ! She is who got me started on making sure I get broccoli sprouts plus other micronutrients ! Also it was inspiring the comment on increase HGH! I way felt it in my workouts this am. I was strong even though I prob slept only 2 hours last night .at the end of the video she did say if we are already 16 hours into a fast and working out it may be better to eat within an hour after . So many variables !


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