Can you get a lot of the benefits of IF simply by engaging in intense endurance exercise? Do intense endurance exercise and IF induce the same nutritional conditions?
Thanks for your excellent discussions of IF and aerobic exercise: I very much enjoyed listening to your conversations with Dr. Galpa and Dr. Panda. I was struck by your emphasis of the point that IF is not about just not putting food in your mouth: the fasted state is a nutritional condition or set of nutritional conditions, which conditions cause and correlates to the benefits of IF. This made me wonder: 1) Of the nutritional conditions induced by IF--negative energy balance, Lack of availability of muscle and/or liver glycogen, mTOR vs AMPK activation, absence of digestive activity inter alia--do ALL of these conditions correlate to the benefits of IF (autophagy, cardiovascular health, metabolic health, fat loss, cognitive benefits, etc.) or do individual conditions correlate to some but not all of these conditions? 2) Which of the nutritional conditions induced by IF can be replicated by intense or prolonged endurance training? Practically, my experience as an (amateur) runner makes me wonder if you could get a lot of the benefit of IF by simply training at a level of sufficient intensity and volume. Fasted long runs of 2 hours or more deplete liver glycogen; high volume training (e.g., 70-100 mile per week for runners) ensures that one is in a negative caloric balance for most of the day; recent studies show that endurance training induces autophagy AMPK activation even when the muscles are in a fed state (even, in fact, when they are fueled continuously throughout exercise). Some interesting studies & references follow below. From a personal standpoint, I am trying to figure out if it makes sense to attempt to shorten the eating window/ engage in IF on top of endurance training or not. What does IF/ time-restricted eating deliver that cannot be duplicated by hard enough endurance training? If I get most of what I need out of just running hard, I may be inclined to stick with that, simply because the IF studies do show small but consistently negative impacts on free testosterone. Thanks again for your incredible clarity, generosity of spirit, and dedication to making us all better every day. Best, Ross Studies: Autophagy, AMPK Activation & Exercise: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5538402/ (Autophagy-Dependent Beneficial Effects of Exercise, 2017) Great review of the mixed findings regarding fasting and cv exercise: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6983467/ (Exercise Training and Fasting: Current Insights, 2020) Another good review on the specific impacts of fasted vs. fed exercise (with variations in feeding time--immediately before vs. 4 hours+ before) on both performance (AMPK & SIRT1) and metabolism (leptin, insulin, etc.): Effects of fasted vs fed-state exercise on performance and post-exercise metabolism: A systematic review and meta-analysis, Aird T, Davies R, Carson B, Scandinavian Journal of Medicine and Science in Sports, 2018 https://paulogentil.com/pdf/Effects%20of%20fasted%20vs%20fed-state%20exercise%20on%20performance%20and%20post-exercise%20metabolism%20-%20A%20systematic%20review%20and%20meta-analysis.pdf