Can we make the problem go away if we fuel with canned worms?
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This is simply not true. Especially when riding at zone 2, most of the energy you use will come from fat.
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This was my thinking. I’ve been listening to alot of Peter Attia’s podcast and his advice is that zone 2 primarily burns fat as a fuel due to the demand placed on the type 1 muscle fibres, as opposed to type 2 that are engaged at higher intensities. Zone 2 also increases mitochondria density which improves fat burning off the bike.
This is what led me to my initial (clearly flippant) question of whether carbs before a ride would negate the fat burning benefits of a zone ride?
Alternatively, I should just stop overthinking and do some riding lol …
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That’s not correct. Your body metabolizes fat as well. You should think of spigots, one for fat metabolism, one for glycogen and then you have your short-term energy stores for anaerobic efforts. So you don’t have to run your glycogen stores dry before your body uses its fat reserves.
It also forgets that your body will use fat reserves to make up for calorie deficits during the day. Or, if you drink lots of soda, it can convert carbs into fat, too, if you take in more calories than you need.
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Not a nutritionist, but is it not a case of CHO in the system has higher oxidative priority than fat?
So, rather than the direct conversion of CHO to fat (de novo lipogenesis), CHO displaces fat as the dominant fuel source, leading to the fat that would have been oxidised now being stored (as body fat).
Happy to be corrected.
So:
What should I fuel zone 2 rides with, on the bike?
I have a couple of longer ones (2 and 4 or 5 hours) planned this weekend. My original thought was to use Skratch Superfuel (almost fully carbs), just at a slower pace than my 100g/hour race pace.
But if the body is primarily burning fat during lower intensity sessions, is there a more appropriate nutrient mix for fueling on the ride?
It sounds like you’ve had a good experience with fasting and it hasn’t effected your performance. That’s awesome. I can tell you my personal experience, and that of everyone I personally know who has tried it, is that fasting and/or keto results in more fatigue, higher RPE, and power loss on the bike. I know some people who have stuck with it because they lose weight, but every one of them says it has hindered their performance on the bike (except one, who says it hasn’t, but his friends all talk about how it has).
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I can second that experience. Trained last year for Leadville with a ton of Z2 fasted rides. Lost a ton of weight and took pride in training my body to use fat. After changing my approach this year, the juice is not worth the squeeze IMHO. I was grumpy, recovery was more challenging and RPE higher.
This year, my FTP is up (300 vs 270 ish), workouts are easier, weight slightly up (5 pounds but I think I could attack that differently), and I’m not nearly as irritable. Fasted is good for losing weight but not so much for training for me.
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Where’s the fun in that!? Welcome to the “thinks about everything twice as much as they actually do it club.” It’s fun here!
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Still just carbs needed. Body has plenty of body fat to mobilize for fuel and can do it at sufficient rates to support exercise, alongside good carb fueling.
This is a good option. You’ll still want high carb fueling for a 4-5-hr ride.
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This does happen. As do about 100 other annoying cellular and physiological processes. I’m glad you brought this up.
Just wanted to offer a clarification and maybe help folks understand how to think about nutrition here a bit.
Making any decisions about anything nutritionally based on one pathway alone is a virtual guarantee for erroneous nutrition strategy.
Reason: homeostasis. There are opposing physiological processes that reverse whatever process a person is trying to acutely exploit, as soon as they cease that strategy.
The best way to make decisions on nutrition strategy is to look at the applied science first, rather than physiology. What makes someone faster? What makes someone lose weight? What are the very basics, boring, repeated so often they’re hated and totally cliché? Those are probably the things that work. Identifying mechanisms like carb burn rates, pathway upregulation, specific hormone responses, etc, is excellent for passing exercise physiology exams, and terrible for making decisions about someone’s nutrition strategy.
@d_diston I hope you don’t feel like I am singling you out at all, and I’m grateful for your post and openness to learning. Please feel free to ask any and all the hard and oppositional questions and I’m happy to help where I can.
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I think there’s a huge variation in what people are talking about when they talk about fasted riding. My personal experience is almost the complete opposite of yours - I and nearly everybody I know who has tried it has found fasted rides to be manageable and beneficial if done right. That includes a lot of the strongest riders/racers I know who regularly do fasted rides. The times when the experience has tipped into being negative have invariably been when people take the view that if fasted riding is good then more fasted riding is better! I.e. pushing the frequency, length and/or intensity of fasted rides. In which case I totally agree that it quickly becomes counterproductive and the negative aspects you mentioned come into play.
FWIW, what works for me (and seems to align well with others positive experiences) is:
- Doing them first thing when your body is naturally carb-depleted (especially if you’ve had a fairly low carb dinner the evening before). Going carb depleted through the day in order to do a fasted evening ride is a good recipe for grumpiness, fatigue, less productivity at work, etc
- Keeping it Z2 or below. I also tend to focus more on HR and RPE than watts during these rides, I’m keeping pressure on the pedals but keeping it fairly comfortable. I’ve known people push up into doing Tempo or SS work and while some have been able to suffer through it nobody seems to enjoy it or get benefits from doing it
- Keeping it to ~2 hours or less, or if riding longer than that then starting to fuel at some point before 2 hours so that the latter part of your ride is fuelled
- Decent meal/snack afterwards (and maybe starting fuelling near the end) to ensure good recovery and that glycogen levels are replenished for your next workout
- Limiting them to once or twice a week. More often than that I think has diminishing returns and fitting them in without impacting the quality of the key higher intensity workouts becomes difficult. Maybe more doable if you were in off season and doing mostly Z2 riding
- Coffee beforehand seems to help lower the RPE and hunger, probably some psychological aspect to this
- A nutritionist friend suggested adding some BCAA powder to my water to reduce muscle catabolism. Probably psychological as well but does seem to make the rides more enjoyable
I also think the gains from fasted riding are somewhat marginal. Almost certainly not worth doing if you’re riding 3-4 days/week or less, you’d be better off using those rides to incorporate more work and fuelling it. Probably not worth doing if you’re still relatively new to riding and making those big early gains. But if you’ve been training consistently for a few years, are starting to see the gains tail off, and are riding enough days and hours that you have quite a few Z1-2 miles on your plan to play with, then I think incorporating some fasted riding can be beneficial. It certainly doesn’t seem to do any harm.
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No worries - appreciate your expertise!
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Agreed. After reading that you’re using targeted fasting one or two days a week, rather than going the full on “low carb lifestyle”, I was comparing apples to your oranges.
If I went full on low carb I think my wife would leave me within a month, I’d be unbearably grumpy!
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Mostly good advice here.
Additionally I’d recommend reading the study on “Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate”
Some citation:
“…When fed carbohydrate, which maintained plasma glucose concentration (4.2-5.2 mM), the subjects exercised for an additional hour before fatiguing (4.02 t 0.33 h; P < 0.01) and maintained their initial R (i.e., 0.86) and rate of carbohydrate oxidation throughout exercise. The pattern of muscle glycogen utilization, however, was not different during the first 3 h of exercise with the placebo or the carbohydrate feedings. The additional hour of exercise per- formed when fed carbohydrate was accomplished with little reliance on muscle glycogen (i.e., 5 mmol GU kg-‘. h-l; NS) and without compromising carbohydrate oxidation. We conclude that when they are fed carbohydrate, highly trained endurance athletes are capable of oxidizing carbohydrate at relatively high rates from sources other than muscle glycogen during the latter stages of prolonged strenuous exercise and that this postpones fatigue…”
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Thanks - great clear feedback!
There is so much in that study. Some of my takeaways:
- the study suggests that feeding CHO does not spare muscle glycogen whereas in the end mentioning other studies that contradict that point. So still some confusion on that aspect
- Feeding CHO does not flip a switch putting you into a stop using fat mode. In fact the picture above shows still big amount of energy used from fat even when fed CHO.
- So even if higher fat oxidation rate when restricting CHO…if taking CHO you’d be able to go longer and so overcompensate overall fat utilized.
- On the other hand…(and that supports the point you made):
- But (for the bigger difference) note “from 80 min of exercise to fatigue”… that’s long into a hard exercise (I can’t imagine 70% VO2max for 3-4 hours (citing:“slightly below subjects’ blood lactate threshold”)
) … so it becomes a balancing act if you go down that path and need to keep upcoming training in mind…
What I ask myself:
- But I don’t even know if one can conclude that let’s say having 10-20% higher fat utilization during some part of a workout effectively results in a permanent change of how your body uses fat for energy (or how many of these sessions would be needed for some permanent effective change)?
- If so…what would be needed to permanently keep that changed physiology? Or would then taking more CHO again reverse that change?
- Is it even sure that having let’s say 20% higher fat utilization during some part of a workout effectively trains the body to use fat better than a CHO fed workout with still good (but just not as high) fat use?
Any input welcome!
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I didn’t read the study, just making some causal observations. In studies when you see VO2max it often means the subjects were hooked up to a gas exchange cart, and they were measuring actual % of maximum oxygen consumption (and not power). Also, blood lactate threshold is often the first threshold, LT1, the aerobic threshold, possibly something in the 70-80% FTP range.
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I’m not an expert, and you should look towards others for a more qualified opinion, but in my understanding fat metabolism remains a very, very significant energy source for aerobic activities.
Here is my understanding of the situation: a combination of fat and weight loss is always coupled to a net energy deficit. But it doesn’t matter much where the energy comes from, provided you stay within reasonable ratios for your macros. So drinking lots of soda will make you fat even though soda does not contain a lot of fat, it is mostly carbs. Conversely, just because you take in a lot of carbs, it does not mean that your body can’t use its fat stores to make up a net energy imbalance, if not during exercise, then for the rest of the day. E. g. it will use lipolysis to replenish your glycogen stores after exercise.
Also, I am not convinced that the lipolysis spigot is turned down significantly or turned off if you demand more power from your body. In my understanding it is that the other spigots are turned up, and thus, the ratio will tip in favor of glycolysis even if in absolute term your fat metabolism hasn’t changed much.
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