Intermittent fasting

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:

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.


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.


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:


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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Well that makes sense. I didn’t know taking in carbs like that will affect the test so much.

So after all this stuff you did…was it worth it? Lol

Not sure I understand your question, what was worth it? Probably nothing I did in competitive cycling was worth it as such, my biggest ever athletic achievement was a 3rd place in a local crit :man_facepalming:. To be fair, I lost to a guy who then went to win gold in Paraolympics in Rio, so could have done much worse :slight_smile:.

Looking at my all time PRs on a power curve, I really am in my element between 1 and 5 minute efforts: 1 minute 9.8 W/kg, 5 minute 5.9 W/kg, my absolute best FTP was just 4.6 W/kg - yet I stubbornly refuse to race crits and instead I target climbing road races, where I don’t stand a chance against 55 kg climbers. The paradox about all this is that reading and knowing more does not make me any faster - I was better off keeping it simple with a clean diet and a small caloric restriction than now, when I feel I secretly hoped IF would be a magic bullet I intellectually know doesn’t exist.

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Well, from analyzing what you said, it just seems like IF didn’t have any profound effects for you. Given that’s the case, I am curious how you felt about your experience. Looking back, is it something you would’ve gone through again? Would you be interested in going even deeper into the rabbit hole and trying variations of IF to try to eek out some marginal gains?

I wouldn’t be too discouraged about your power curve. It’s certainly possible to get those adaptation and epigenetic changes you seek but that stuff may take years. Yea, as you approach your upper limits those marginal gains get harder and harder. :sob: Did you have any professional coaching while you were doing all this or you did it by yourself?

i’ve actually been struggling lately once I start eating after my fast. It’s like the flood gates open and can’t get enough. kinda defeats the purpose of IF… smh

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If you find that IF is leading to overeating then any of the related benefits (insulin sensitivity, nutrient partitioning, improved cognition & focus etc) are probably going to be trumped by a decreasing w/kg and increasing waistline :see_no_evil:

Standard tips for increasing satiety (waiting 15-20 minutes between courses, drinking plenty, decreasing food variation, switching off distractions etc) will all help.

yeah. need to get my head out of my a$$ and get back on it.

There are lots of ways to ‘bulk up’ meals with low energy density sources if you want to feel like you’ve eaten lots but with a bit of damage control on the caloric intake. I would heed a bit of caution though…

Having fallen down the slippery slope myself of chasing that ‘totally stuffed’ feeling which is a bit like a carrot on a string. Ultimately it’s eventually unobtainable as you become conditioned for larger and larger meals, not to mention dysfunctional.

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Sort of my experience as well. In the beginning all was fine with IF. Highly motivated. And it was sort of cool of being able not to eat for such an extended period. And this got better and better.

However, after while I experienced exactly the same: flood gates open.

Now I have breakfast again. Later than before, though.

I’ve started that this week to see if it helps. so far no, but i’ll give it a little bit more before I decide to stick with IF or just go back to trying to eat clean meals. I never really felt much difference between eating regular meals vs IF though. No worse and no better…

I followed it for a few months.

If you are eating different foods, as alluded, then it’s going to have differing results on satiety and hunger signals to that of simply shifting your existing nutritional intake & the eating window.

I have no objection to eating processed “fun” foods, in moderation. After all life is short and food shouldn’t be just a simple means to an end, it’s social, cultural and more than just fuel.

If you find that you can’t turn off the tap on these foods though for whatever reason they would probably be best avoided. I don’t agree with restricting the foods you enjoy or want from your diet but can appreciate that for some people self control & willpower can be hard to come by.

Okay, now I understand what you meant, thanks for clarifying! At the moment, the gains I’m seeking are very substantial and by no means marginal :slight_smile:. I’m back to eating meals more often but I will incorporate 1 or 2 fasted rides in my weekly schedule, definitely in the base phase.

I did have a coach back in 2016 season, annoyingly I have to admit this was when I’ve had my best results, self coaching lead to peaking too early.

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