Fasted workouts is not recommended for cyclists and endurance athletes

@bkolden asked about my opinion on exercising on a fasted state. In summary, I do not recommend doing workouts, long rides or events on a fasted state.

Please see this post for an overview of this topic.

Below are links to the several position papers, all of which have in common the recommendation that athletes practice adequate energy intake for intense training and competition:

Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine

American College of Sports Medicine position stand. Nutrition and athletic performance.

International society of sports nutrition position stand: nutrient timing.

A more recent study that looked at several other studies on the subject of fasting and endurance sports concluded that:

" This review of the literature identified that the effects of fasting on endurance athletic performances requires further investigation. Different fasting programs influences human physiological and biochemical parameters that are important for athletic performances. The collective data suggest that different fasting practices (ICR, ADF and TRF) decrease body weight and fat7,27 in both trained and untrained subjects. Moreover, several studies demonstrated that fasting alters protein, lipid and glucose metabolism and associated hormonal responses. However, the conflicting findings related to glucose metabolism in response to fasting in highly trained athletes require further investigation. Studies on the effects of fasting on indicators of physical performance have generated conflicting data. For example, some studies reported decreased performances while others showed no effect. There are a number of reasons for such differences, including variations in experimental design, fasting duration, and unique participant characteristics. We suggest that athletes train at relatively low intensities (and not at high intensity levels) when fasting to ensure that they recover adequately to optimize performances in competitive events. Our analyses also revealed a major weakness in that most fasting studies recruited sedentary subjects or low-level athletes, often without well-matched controls. We recommend that well-controlled studies are required to improve our understanding of the effects of exercise in fasting athletes, and to help uncover novel insights into the mechanisms driving changes in energetic pathways and physical performances in trained endurance athletes that choose to fast."

Aside from studies, here are a few articles from popular media:

Why Intermittent Fasting is Worthless for Endurance Athletes


This was a topic that came up early on after I started with @Coach_Theia last year. I’ve never been big on the whole fasting concept and usually need a little something especially before a substantial ride or workout. I started thinking more about what i was eating and noticing how it made me feel. I found that for an hour bike workout, a couple tbsp of maple syrup works great - if its longer or a harder effort, I’ve taken to having a little protein along with the carbs. I can get by with an energy gel but its not as good. For a gym workout the energy gel seems to work fine.

If you’re someone that has followed the whole fasting WO idea, i would read the info from Coach and then really try a few things and take notice in how you perform - you may be surprised at how much better it goes with even just a little healthy nibble beforehand.

Thank you for sharing these; I had a rather epic discussion with my trainer a while back on this topic. It’s especially a no for those with thyroid struggles; at least in my experience. Look forward to reading these!

Friday is still pending… in final rounds; been a bit hectic. Did 4.2 yesterday (oops, read the thread after.)

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Thank you for this information! I look forward to reading the articles. A very weak area for me is my diet. lol. Need to get it under control if I want to perform better.

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Thanks for sharing this @Coach_Theia! I regularly see posts on strata from friends who note that these are “fasted” efforts, and was curious. Not for myself, of course; I need to eat all the things :joy: It never made much sense to me, but then I’m much more of an all things in moderation kind of person. I just always feel better with 3 meals, and the last year have tried to push to far less empty calories and carbs in favor of healthy options. For example, I’ve maintained a weight loss that was initially obtained through heavy reliance on capping calories to now just eating way more veg and smaller portions of carbs. I’m a vegetarian (eat dairy and eggs, though in smaller quantities than I used to). So for me, a breakfast with some protein and whole grain carbs is essential before any efforts! Don’t think I could ever go full vegan, but gosh do I feel better since reducing my intake of cheese in favor of more plant proteins.


@Coach_Theia I’ve been doing intermittent fasting - 16-8 intermittently (haha) (usually 6pm to 10am or 7 to 11) for the last several months. I like it – it is an easier way for me to manage my caloric intake, and i have a fat loss/weight loss goal. I never thought of doing it for performance purposes. I have lost weight and am no longer pre-diabetic so I would say the health benefits and weight loss benefits will keep me doing it. I’m not a professional athlete, and although I want to improve my cycling, I also have other goals.