Intermittent Fasting

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  • #27439

    I know this is sort of the “trendy” thing to do now, but I’m curious on the UA take on this method.

    I already do some fasted runs during my week (usually those that are 1 hour or less) but if I am running for 1.5-2.5+ hours I’ll have a small bar or a PB&J beforehand.

    In the intermittent fasting methodology, how are the long endurance workouts handled? I was thinking of making exception for those instances, or perhaps fasting the evening afterwards instead.

Posted In: Nutrition

  • Moderator
    Rebecca Dent on #27440

    Hi Briguy,

    Thanks for your question. Just to be clear, are you asking a question regarding how long you are to carry out your endurance workout fasted and/or are you asking about when to carry out intermittent fasting in addition to your fasted training sessions?

    I will then answer your question fully.


    Rebecca UA Dietitian.

    Rebecca Dent on #27441

    Can I also ask, what is the reason you are carrying out intermittent fasting? Thanks

    briguy on #27442

    Hi Rebecca – For the first question, I think I am mainly asking how intermittent fasting is executed when there is a long/intense workout scheduled. For this, I’ll define “intermittent” as the common/current version of a 16 hour fast each day (typically 8pm to 12pm the following day).

    As to why, I have a stubborn 10 lbs above my typical training weight that I gained following a surgery in mid 2018 and that I am struggling to lose despite 6+ months of pretty steady training. I’ve gone “hard core” in the past with calorie-counting etc and lost weight but frankly that method is extremely tedious and I’m looking at another method that’s working for some of my training partners.

    Aaron on #27737

    I’m curious too on this question as I’m interested in caloric restriction for weight loss this winter during transition /early base phase and I think healthy diet + some intermittent fasting is my most likely sustainable approach.

    Rebecca Dent on #27766

    Thank Briguy for your answer and welcome Aaron to the conversation.

    In short, creating an energy deficit regardless of dietary method (Intermittent fasting, ketogenic diet, paleo, vegan, even weight watchers) will help you to lose weight. I would not necessarily advise intermittent fasting if you are already carrying out fasted training sessions. Research has shown that extended periods of time spent being in an energy deficit via nil food intake (in addition to fasted training) through out the day can have resulting negative consequences on training quality, training gains, recovery, performance and health (increase cortisol – stress hormones, reduced testosterone, reduce immunity, increase risk of injury/illness).

    As you have highlighted Briguy it sounds like you are struggling to adhere to the IF and so perhaps creating an energy deficit via an easier method would be more sustainable. Often UA clients I work with do really well at adhering to good eating practices through out the week, but then relax a little at the weekend, e.g. increase alcohol intake, relax on restrictive eating, go out to dinner /social activities that lend to eating more. This then can offset the energy deficit created in the week and result in energy maintenance and no or little weight loss achieved. Can you determine small changes via keeping a food diary to help you reflect on what you are eating (as you again highlight by recording your calorie intake you established weight loss via this method, but you don’t have to count calories to achieve weight loss). Again showing you do not perhaps need to IF if you can create an energy deficit via simply cutting out or down on foods. There are simple and effective dietary changes you can make that can be implemented to help achieve sustained weight loss maintenance (often the hardest part of the whole process, keeping the weight off) but also dietary changes that can help alleviate muscle mass loss when you lose weight. When clients implement dietary changes advised via the custom nutrition plan, they often report to feel leaner and achieve weight loss (if desired).

    In summary I would not recommend IF in addition to carrying out fasted training sessions. If weight loss is desired then I would advise to create an energy deficit via simpler methods e.g. find the easy wins to create an energy deficit e.g. reduce alcohol intake, cut out any processed foods e.g. chocolate etc (if present), reduce portion sizes, use less oil when cooking, avoid being heavy handed when using butter.

    I hope this makes sense and answers your question?


    briguy on #27821

    Thanks for the detailed response Rebecca!

    The fasting I have been experimenting with is the typical 8pm Day1 to 12pm Day2 fast window. Where I struggle with it is, you guessed it, when I do a fasted workout in the AM of that Day2. A workaround I have been trying instead is to the morning workout still fasted, but then if needed (with any long and/or intense workout) fuel right afterwards and continue to eat normally for 8hours of that particular day, and then start the fast at 4pm that day instead, fasting until the next morning at 8am. Essentially, a time-shift of the fasting window.

    I know this isn’t really what you’re espousing above, I’m just documenting here for discussion purposes.

    Rebecca Dent on #27829

    From what I understand you are shifting the fasting window to incase your fasted workouts. It is only recommended to carry out zone 1 and zone 2 sessions fasted (low intensity work outs), it is not advised to carry out any strength based sessions fasted as you do require carbohydrate to fuel those work outs and get the most out of this session. I see no benefit to your fasting windows other than restricting your eating to a set period of time to potentially create an energy deficit. Are you losing weight? If you are still eating to your calorie requirements within that time window you will not lose weight. I would focus on actually ensuring timing of nutrition around your training is optimal to maximise training quality and adaptations of that session as opposed to focusing on creating a window of fasting. I still think you are spending too much time in an energy deficit when carrying out long sessions fasted and then fasting again from 4pm. Without knowing exactly what your training schedule looks like and your nutrition intake I am unable to provide more precise recommendations to you individually. You can always sign up to the custom nutrition plan for more guidance Thanks Rebecca

    ian_gunn1 on #47049

    I realise I am incredibly late to this discussion.

    I have also been restricting my eating window a little (not sure if it qualifies as IF), and I routinely do fasted workouts in the mornings, no problems. But these are always Z1/2 and I always eat well a couple of hours before strength or other hard sessions. Many of the benefits of fasting (IF or longer) such as autophagy are not related to training so much as general health and longevity. Perhaps we have to decide on our priorities, shorter term training for mountains, or longer term general health?

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