Carb loading info wanted

Nutrition
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@Nate_Pearson’s mentioned this several times on the podcast, and I’d like to read more about this and the science/studies (or summaries thereof) that back up the various protocols. I want to know not only
what to do, but why, and some evidence to back that up.

Anyone have links to more detailed info on this?

Thanks!

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I’m also interested in this, I have believed that carb loading was a waste of time, glycogen levels were finite and when you tried to cram more in all you ended up doing was increasing water weight and fat making you slower.

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Here you go!

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Reading that is it not just saying that you are only trying to normalise glycogen stores? Surely you aren’t normalising glycogen stores by eating the incredibly impressive amount of food you described on the podcast?

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Just skimmed it, but from the linked paper:

For triathlons lasting longer than 90 min, supercompensation of glycogen stores may be beneficial and can be achieved by most well-trained or elite-level athletes in the 36 to 48 h before competition by increasing dietary CHO intake to approximately 10 to 12 g·kg−1·d−1 (49).

And from reference 49 (based on search for ‘12’) I found:

  • :black_small_square: A primary goal of competition nutrition is to address nutrition-related factors that may limit performance by causing fatigue and a deterioration in skill or concentration over the course of the event. For example, in events that are dependent on muscle carbohydrate availability, meals eaten in the day(s) leading up to an event should provide sufficient carbohydrate to achieve glycogen stores that are commensurate with the fuel needs of the event. Exercise taper and a carbohydrate-rich diet (7–12 g/kg BW/d) can normalize muscle glycogen levels within ∼ 24 hours, while extending this to 48 hours can achieve glycogen super-compensation.

Table 2 from the above also says “36-48 hours of 10-12g/kg bodyweight per 24 hours” for carb loading. It also has references to other papers I haven’t looked at.

Tons of interesting stuff in this paper with references, I guess I’ll be busy for a while.

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This is why I tried to do 10ish g/kg for my carb loading.

That paper’s really cool. I think it’s worth a read.

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OK, I haven’t ready the whole main paper, but have been looking for the source of the 10-12g/kg/day carb loading recommendations.

After following a few citations, I think this is the (or one of) the papers. One thing I noticed was not only the amount of carbs, but at least in this study they were specifically high glycaemic index carbs. As @Nate_Pearson mentioned on the podcast, it’s hard/impossible to eat this many carbs from ‘good’ sources.
Since eating like for the first time right before an important event is not a good idea, I’m planning to give this a try to see how my body reacts. I don’t expect to be able to ‘feel’ the glycogen stores, but I want to make sure this doesn’t make me sick :slight_smile:
I’m looking at needing to eat 700-800g/day, which is about 3 boxes of Pumpkin Joe’s Os. I don’t normally track my intake, but for this I plan to log/weigh what I eat so I know how much and what I ate, so I could repeat this again. Or not repeat it, depending on how I feel…

https://www.researchgate.net/publication/11267836_Carbohydrate_loading_in_human_muscle_An_improved_1_day_protocol

Abstract:
It is generally acknowledged that even without a glycogen-depleting period of exercise, trained athletes can store maximal amounts of muscle glycogen if fed a carbohydrate-rich diet for 3 days. What has never been examined is whether under these conditions this many days are necessary for the content of muscle glycogen to attain these high levels. To examine this issue, eight endurance-trained male athletes were asked to eat 10 g.day(-1).kg(-1) body mass of high-carbohydrate foods having a high glycaemic index over 3 days, while remaining physically inactive. Muscle biopsies were taken prior to carbohydrate loading and after 1 and 3 days of eating the carbohydrate-rich diet. Muscle glycogen content increased significantly ( P<0.05) from pre-loading levels of [mean (SE)] 95 (5) to 180 (15) mmol.kg(-1) wet mass after only 1 day, and remained stable afterwards despite another 2 days of carbohydrate-rich diet. Densitometric analyses of muscle sections stained with periodic acid-Schiff not only supported these findings, but also indicated that only 1 day of high carbohydrate intake was required for glycogen stores to reach maximal levels in types I, IIa, and IIb muscle fibres. In conclusion, these findings showed that combining physical inactivity with a high intake of carbohydrate enables trained athletes to attain maximal muscle glycogen contents within only 24 h.
(PDF) Carbohydrate loading in human muscle: An improved 1 day protocol . Available from: https://www.researchgate.net/publication/11267836_Carbohydrate_loading_in_human_muscle_An_improved_1_day_protocol [accessed Oct 03 2018].

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This gets to one of my questions. My triathlons seem to go about 2 - 3 hours. I had no idea if carb loading would help for this shorter time period. Next season I will have to try it.

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OK, I read the whole thing - it’s not that long at 6 pages, and quite accessible. (I did skip the description of the muscle biopsies and staining - that is over my head.)

Some things I thought were interesting:

  • The participants exercised the day before the carb loading started. This was supervised, so they all did their final training session at some point the day prior to the study starting. It was not discussed if this was important, other than the subjects specifically not exercising the morning the study started or during the study. Since other carb loading protocols involve workouts just prior to loading, I wonder if 48 hours of rest before carb loading would make a difference.
  • The increase is glycogen is quite significant 95 to 180 mmol/kg wet mass. Other carb loading protocols get in the range of 160-200. The graph shows a slight increase from the 180 to the day 3 measurement, but from what I gather this wasn’t statistically significant.
  • They reference other studies that show muscle glycogen remains high when at rest, so this protocol could be done a few days before the event, as long as there is no exercise between the loading and the event. If carb loading makes you feel bad, you could do it a day early.
  • the subjects were provided a liquid maltodextrose-rich beverage (Polycose), and also allowed to eat their own high glycaemic index foods. No mention of the proportion of these actually eaten was mentioned. I don’t know how important this is - I think it’s likely the glycaemic index is more important that the source being maltodextrose.
  • They hypothesize that the reason multi-day protocols are required with depletion workouts is that since they start out at lower glycogen levels, it takes longer to build up to the same levels. You can only synthesize glycogen so fast, and in reality you not eating the whole 24 hour period.
  • The 24 hour period went morning to morning, so starting this the morning the day before the event is early enough.
  • There was mention of another protocol that started with a 3 minute maximal effort immediately before the start of 24 hours of carb loading - it would be interesting if that protocol showed better results. This would require that hard effort the day before the event, which could be counter productive.

I’m going to give this a try starting tomorrow morning. Not really looking forward to having to each so much simple carbs all day long…

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OK, I did this and ended up with about 800 grams of carbs during the day, most very simple. The study tested high glycemic index carbs, so I tried to stick with that. It was not fun eating that much ‘junk’, and I felt bad (unsettled stomach) for a few stretches during the day. I slept fine, and felt fine the next day, and did 4.5 hours on the bike, and felt good there too.
I had a salad and some sweet potatoes for lunch, but that is about all the ‘real’ food I could fit in and still eat enough carbs - there is not much room for anything else.

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I don’t why it’s hard to eat that much for you guys. It’s like a kg of carbs for the whole day if you weigh 80 kg? That’s not a lot? What am I missing?

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It is actually a lot to eat of just carbs - it’s doable, but it does take work. It would be fairly hard to get this eating whole foods - I think starchy foods like potatoes/rice would be the only way to do it with whole foods.

For example, you could eat two family size boxes (38 servings) of honey nut cheerios to get the required carbs.

(760 grams total)
or 3 18oz containers (39 servings) of oatmeal:

(897 grams total)

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The key to delaying the satiating effects of eating such a significant helping of any macronutrient is to vary the sources.

Much like being stuffed to the brim with Sunday roast the ‘dessert stomach’ always has room for another course :wink:

1000g of carbs from a single source or 200g from 5 different? Not to mention the wider vitamin/mineral profile too :sunglasses:

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Yup, completely agree - I did not attempt to eat that much of one thing, but those examples help visualize just how much food this is. Keep in mind that 200 grams of carbs from oatmeal is still 2/3 of one those containers :slight_smile:

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I must admit, when I load before a race I have no problem at all with eating 10-12g/kg. Quite to the contrary. I don’t find it that much either.

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OK…so I picked up 5 kgs with my carboloading. It hurt as hell as I was dropped up the first hill (race started with a loooong ascent). It was 170 km race and I did manage to claw my way back to finish 17th / 48 in my group. It was 40degrees Celsius (104) at the peak.

In the end it was much tougher to hit my carbs. I also went to the loo the evening before the race, when I woke up, just before the race AND after the race. The behemoths I birthed was spectacular.

Next time I will rather try and carboload with drinks. I though I was a big eater, but feeling uncomfortably full for two days wasn’t a great experience.

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@faniefiets - thanks for sharing your experience - I just did the one day of carb loading and also felt uncomfortably full for a fair portion of it. I’ve only looked at the one study that Nate mentioned on carb loading (the carb loading study that the meta-study referenced), but it studied high glycaemic index foods, with the provided food being a drink. It’s possible that carb loading works with low glycaemic index foods, but it seems that many studies have focused on high glycaemic index foods.
I didn’t do sugary drinks, but had lots of cookies, chocolate frosting by the spoonful, cornbread with lots of honey, etc with very little ‘good’ stuff mixed in. Even with this very carb dense food, I had to be focused to eat enough. I tend to eat lower carb normally (really just mainly avoiding processed grains), so this was way different than my normal diet.
When I get some time I want to read some of the studies on carb loading and see how they compare.
It may be that high glycaemic index foods are used in the study because that allows most subjects to eat enough, rather than there being a carb loading mechanism that requires high glycaemic indexes. This is kind of the same reason studies don’t use repeated 4 hour trainer sessions - you won’t get subjects to do this kind of thing.

Quotes below from: https://www.researchgate.net/publication/11267836_Carbohydrate_loading_in_human_muscle_An_improved_1_day_protocol/download

Each subject was required to eat
10 g/day–1/kg–1 body mass of high carbohydrate foods having a
high glycaemic index for the next 72 h, to keep a dietary and
physical activity record, and not to engage in any physical training.

In line with previous recommendations (Lamb et al. 1991),
compliance by all subjects with the carbohydrate loading diet was
achieved by providing them with maltodextrose-rich beverages
(Polycose, Ross Laboratories, Columbus, Ohio) as the predominant
source of carbohydrate.

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Here is what seems to me to be a wise summary of what is the current state of knowledge about nutrition and performance:
Swifter, higher, stronger: What’s on the menu?

  1. Louise M. Burke1,2,*,
  2. John A. Hawley2

Science 16 Nov 2018:
Vol. 362, Issue 6416, pp. 781-787
DOI: 10.1126/science.aau2093

It can be read online or downloaded as a pdf from:
http://science.sciencemag.org/content/362/6416/781

All I can say is: it all seems very confusing!

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I thought eating 800g of carbs would be fun. It’s not.

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Eating 300g of carbs is fun. By the time you get to 600g the fun is well & truly over.

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