Intermittent fasting

Wow, thanks for all that info. Very interesting! I found this anecdote to be telling along with your diet and heart rate changes.

This sounds like you’re not fueling enough for your workouts.

How are you timing meals and macros with your training rides? Are you riding fasted most of the time, all the time, or not much?

With the heart rate stuff, it sounds like you’ve changed a couple of dietary things that would contribute to higher HRV and lower resting. Less alcohol, less simple carbs, IF will all contribute.

Have you tried fast carb supplementation during training? Was that IF for 7 weeks? If so that may be overkill. Some of the benefits of IF is to stimulate autophagy but once you go past that you might be compromising your training. Having enough fuel for quality workouts is usually the higher priority. The weight loss comes with a higher quality diet. Periodized IF is more like icing on the cake here.

Thanks for your reply @Minty_One. To answer your questions:

  • 2 fasted rides a week (in the morning, followed by lunch at noon), I did all the other rides in the late afternoon, 2 hours after the last meal.

  • IF for full 7 weeks indeed, I slipped a couple of times due to life commitments but in general it was super easy and I feel I could definitely do this nearly forever, I don’t miss my breakfasts.

  • I’ve consciously not done any fast carb supplementation during training, just abstained from simple carbs altogether. I was also significantly dropping my training volume at that time, so the longest intensive workouts were like 90 minutes, I did not feel carb deprived during those.

All in all, I think IF may be very helpful in some cases, but it’s pretty much a personal thing - fasting and eating to hunger seems to work less than ideally for me, as I will replenish the caloric deficit no matter what, doesn’t matter how long or short the eating window is.

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Thank you for sharing your experiences with this! I tried intermittent fasting for a couple of weeks in 2017. This was also after having read the obesity code.

I feel like my experience with the results is somewhat similar to yours. Especially during the beginning I didnt find it that hard to skip breakfast. Only sometimes I ran into issues with late night training → late night snacking/“recovery meal” → keeping 16 hours fasting window afterwards, well into the afternoon.

Like you, I also noticed that I don’t have much issue eating all the Calories in 8 hours. After working out, I would regularly be able eat a 1200-1500 Cal. lunch.
Now I’m back to splitting those between breakfast und lunch and actually doing somewhat better with hunger management, and especially regarding performance on the bike. What I still took away from the Obesitiy Code were the general insights into insulin (resistance). I try to not eat anything after 8 pm and before breakfast and also limit snacks between meals. Together with generally high diet quality this enables me to keep a deficit. I adjust this as necessary, i.e. big lunch planned at the office equals light breakfast.

Regarding the findings by Dr. Fung or the “carbohydrate-insulin model” in general: There is some controversy around it, like with all things nutrition…

Stephane Guyenet (who is the author of a very interesting nutrition book himself: The hungry brain. Strongly recommended, also looks at underlying factors like palatabilty of food and societal factors that make people overeat) wrote this article: Why the carbohydrate-insulin model of obesity is probably wrong - which does not reference Dr. Fung directly but debates a lot of the reasoning he uses in his book, like the harmful effects of carbohydrates in general and the Glycemic Index/Load.

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Thank you, this is very interesting. I did not know of Stephane Guyenet before, I’m definitely going to check his article now. I guess there goes my productive work afternoon :slight_smile:.

Hrmm, with what I can gather you would’ve been an ideal candidate for losing some %bf from IM and with 7 weeks, there would’ve been results. Given all the data provided, I do think there’s something you can optimize here and that is to periodize your feeding. Rather than focus on the hours without food and eating to hunger, really let yourself get hungry and then, go past it. Usually, there is a dip to overcome but once you get to the other side, the urge to eat disappears. Generally, most of us have enough fat stores to last a few weeks to a month without food, so eating is somewhat of an option.

One of the tricks to IM and weight loss is that, for most people, it’s a way to decrease caloric load whether they’re conscious of it or not. If you are doing a complete refuel and, with the lack of progress on the %bf front, you may stand to gain by doing a tangible caloric restriction through fasting.

The periodized part of this method is on training days you only fuel right before your workout. So, for example, when I do a late afternoon workout I am abstaining from food all morning until mid afternoon, about an hour or two before the ride.

If there is anything to be gained from this, it’s this! You have trained your body to be more resilient in the face of liver glycogen depletion. Although this is not the same as muscle glycogen depletion, as I assume you are eating carbs the night before, this type of resilience is useful in fighting that mental “bonk” feeling. The trick is, on longer rides and races, you have to be extra diligent in proper fueling.

All good points! Just to clarify and correct your assumption: I currently do 2 fasted rides a week, Wednesday is a shorter (60-90 min), carb depleted ride after an intensive Tuesday workout with just protein and a salad the night before (e.g. salmon and spinach). Saturday is a longer (2-3 hrs) fasted ride with moderate carb intake the night before. I already posted in another thread on how well it worked out for me 2 seasons ago and it’s really good to see how quick is it to regain the past adaptations.

Back in 2016 the first 4 weeks were a struggle, this time it all came back after literally 1 ride. The second workout was just fasted, not depleted - I was planning to do some easy endurance but legs felt great and I ended up spending 25 minutes above threshold out of 2,5 hours of total workout.

I definitely see the added value of fasted training and will keep doing it during my base phase, but I think I will just stick to clean food and normal meal schedule on the remaining 5 days of the week. I have quantifiable results that this approach worked for me in the past (that fat oxidation curve from my topic really speaks for itself), I was just hoping that IF would make even a bigger difference but that’s not really what I’m seeing in practice (based on my own example).

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Ah, so you did go for muscle glycogen depletion too! Well it looks like you covered a lot, especially with all that data in your other post. It’s too bad that you don’t seem to be a high responder to IF. Were you trying to lose body fat with your protocol?

I’m curious , how come you were doing so many fasted rides (>90%) in 2016?

This guy should no a thing or two about fasting and nutrition on a bike.

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Yes, mostly trying (and succeeding) to lose body fat.
Long story short, I had a bike crash during training and spent the subsequent months not being able to ride my bike due to a hand surgery and complications. I saw this as an opportunity to focus on weight loss, started with the Racing Weight Quick Start guide where I learned about the benefits of occasional fasted workouts. It reacted to this training pretty well and found myself not needing to fuel before my workouts and due to being indoors they were short enough not to require fueling during.
I don’t recommend this approach to anyone - this really caused me a lot of trouble when I finally could do long intense rides where carb supplementation was essential.

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Yea I saw in the other thread, it seems like the sacrifices of being more fat adapted may have sacrificed your carb absorption/utilization abilities. I saw the charts and calculations, which seem accurate but it just doesn’t add up to me. I didn’t even know that was physiologically possible to use that little fat. Sorry :frowning_face:

I really would question it. You’d expect to see some low% of fat but not 0 at the low efforts. You’ve got some power in you so you have to be well trained and to be so carb heavy, that’s nuts. If everything about those results are true, are you thinking that your low hanging fruit is to work on utilizing fat as a fuel? This would be a multi month/year experiment, but I wonder what would happen if you went keto. If your baseline is really so carb heavy, what was your lifetime diet like? I find this…fascinating…

I tried Keto [almost zero carb] for a while. Lost a lot of power and HR was much much higher thru the rides. Back to a slightly reduced carb diet with intermittent fasting now.

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Yes it’s interesting that he is following this approach. Especially as he probably has some of the best advise and coaches in the world to help him. I wonder if trainer road could get sir Dave on the podcast one day!!:thinking:

What a brilliant idea. Any chance @Jonathan?

That looks about right. The direction of the community has been to time carbs and to earn your carbs. I like carbs, therefore, I bike :joy:

I see people referencing the Obesity Code by Dr. Jason Fung, but I feel that th Diabetes Code is a bit more relevant. Both books can be summed up in like 3 pages though. :grimacing:

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I triple checked the formulas after seeing the initial result, I get where you’re coming from. My results were probably affected by me eating an energy gel 30 minutes before the test and drinking an high carb drink mix just before the test. You need to remember I wasn’t doing this as an experiment, it was just part of my annual medical checkup for the racing licence, I simply wanted my ramp test to go as good as possible as I knew I wasn’t in my best shape at the time :).

Here’s the article examining the effects of pre-excercise glucose/fructose ingestion on fat oxidation rates:
https://www.physiology.org/doi/full/10.1152/ajpendo.1997.273.4.E768

The test in 2017 was also not done fasted, but I did it 2-3 hours after lunch. Safe to say 2 different nutrition approaches must have had an effect, but even though it did, the subsequent experience from my longer rides proves I was definitely very much carb reliant in 2018.

So if anyone is planning to do a similar test to check their fat/carb oxidation rates, I strongly advise choosing one approach regarding pre-test nutrition and sticking to it, I think it makes sense to fuel the same way as you would for any other short workout.

Definitely, I will stop with IF every single day, but I will keep my two sessions a week fasted. The effects are really immediate and I find it super easy to switch. Did a 3 hour fasted ride yesterday, 2100kj in total, it felt easy and after the ride I did not get that carb deprivation/ravenous hunger that I would be getting normally.

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This is the exact reason why I don’t have a lot of trust in these met tests. Did several myself, got always told that I have virtually no fatox according to these tests. However, I can go out there and ride for 6 hours without any food intake and do just fine. Came across this review paper (section “Nutrional Status”)

Ever since I don’t believe in these tests anymore. Too much impact by pre-test food intake. And all the studies were run fasted. I don’t race fasted. Furthermore, these tests take into account the first 45min only. But what about after 2 or 3 hours? The sources for energy will change as stores empty. This is not reflected by these tests.

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I started to read the article on fat oxidation but I’m nit sure how relevant it is. The amount of carbs consumed 1 hour before exercise at .8g/kg body weight would mean I would take 3.5 x 20g gels of pure glucose 1 hour before cycling. It seems quite a lot to me.

I’ve been doing low carb with some IF for the last couple months. Like most, I find that anything too close to threshold, or above threshold for any significant time is very hard if not impossible. I’ve done a little bit of experimentation with carb supplementation around training. My protocol (which makes it sound WAY more organized that it actually is) is to time backwards 15 minutes from the 2nd or 3 set of High Intensity intervals and take a gel then. I find the first set of intervals is a gimmie, even with fasted resources. Its the 2nd or 3 set where I fail, so I’m supplementing just enough, just before, to allow me to eeek out those sets. If I fail on the fourth + sets I figure who cares, I’ve got the lions share of the benefit of the intensity work.

I know strict calorie math does not apply in the hormone theory of diet and exercise, but I figure that glucose hitting the bloodstream right when the muscles are screaming for makes this little diet violation a non-factor in the big picture.

As far as the IF goes. I find that a 16/8 fast is so easy it doesn’t seem to count. Really, when you look at the that kind of eating window, qualitatively its really no different than the advice to not eat right before you go to bed. My goal is to do a couple of 18/6 and a couple of 20/4’s every week, weekdays (when I have a lot of control over my schedule). Stick with low carb (no sugars, no grains) meals during the week. And then be a little less strict with both carbs and eating windows during the weekend. I live in California but work east coast hours so the IF basically means I don’t eat till after work. I’ve gotten used to the idea that being hungry is just a slight additional misery added to the work day. :wink:

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You’re right, pre-test food intake will have an influence on the test result, same as a pre-test long endurance effort would. But I wouldn’t go as far as to say the tests are not reliable - they can be useful to establish a baseline as long as we’re consistent with nutrition, hydration, rest etc before the test.

There’s a 4-8 week adaptation time before you can work out at previous intensities*. Also, More salt. Keto is diuretic so blood volume is reduced, and one side effect of hypovolemia is increased heart rate.

(*) which is why every short term keto study keeps “proving” carbs are necessary…

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