I missed the part where they said the low-carb athletes performed better...Oh wait, they didn't.

The next interesting part is where they implied that this was a new idea. Well is a new idea something that people thought of 20 years ago?

My extremely limited knowledge on this subject is that fat and glycogen are two different ways to store energy (with some different uses for sure but also overlapping in some ways as just a place to store energy). So, it makes perfect sense to the uneducated mind that if you can more easily burn fat during endurance efforts, you now have a larger total source of available energy than if you can't get at your fat as easily and are limited to relying more heavily on glycogen. {edit - I have no idea if diet can affect this but I have seen many references to specific types of training claiming to improve one's ability to utilize fat. I kind of think we are all already on this without really realizing it}

http://www.humankinetics.com/...yrsquos-fuel-sources

That it is a legitimate way to fuel for those of us who are low-carb for other reasons, maybe. I am diabetic, for instance, and therefore low-carb is more than just a lifestyle choice.

So, it's been decisively shown that changing your diet can change substrate utilization; but on the other hand it has not been shown that these same people perform better in competitions or time trials lasting up to 3 hours. Is that right?

Since this was one on ultrmarathoners, the next question is, do ultramarathoners do better on a low carb diet. I am willing to believe that the reason that performance improvements have not been found yet is that the tests weren't long enough for the advantages of fewer carbohydrates needed to show up. Though I will need to be convinced.

I think as far as ultramarthons and races out past 6 hours are concerned we may be in an "absence of evidence" situation rather than "evidence of absence". Hopefully the next study in the pipeline addresses performance out to ultramarathon length.

I completely agree and was hoping the article would comment on performance but it didn't. They may in fact perform better, I'd like to know either way.

I also didn't see what the test subjects ate during exercise. There may be some low carb/higher fat food that works well with these people but again they didn't comment.

50 miles would probably take me near 10 hours or more. I would think that at 11 min/mile I would be able to eat just about anything whether it is high fat, protein or carb but I've never done it so I can only speculate.

I don't see how both of the statements in red can be true unless the carb-restricted group covered more distance (hence greater total caloric expenditure) in the three hour endurance run than the non-restricted group. If this is the case, there is indeed a performance benefit, as they were able to run further at the same effort, in the same amount of time.

I am definitely no expert in this, thats why I brought this topic up. The only things I could see being a beneficial product of low carb on ultra length events would be a steadier blood glucose, the need to consume less calories, less gastro intestinal distress and less blood diverted from working muscles to stomach.

I still haven't heard what the benefits of burning more fat is.

I dont see the correlation, if your talking about the statement that they burned twice as much fat, they are speaking in ratios of fat/carbs not overall calories.

If you look at this as just simply X amount of energy is needed to get from here to there in Y time at a steady pace, it may not make much of a difference WHERE you are getting the energy from as long as you have enough. For steady state races, that may be as far as you have to go and (being a bit simplistic) it does matter if you get that energy from fat on board or by eating lots of gels and energy bars.

But, fat and glycogen are not equivalent since they are used differently and for periodic sprint or higher effort levels, you need glycogen. Glycogen can be in short supply, at least on a minute to minute basis, and it not quickly replenished.. So, it would seem to me that it would be an advantage to maximize your ability to burn fat, and thus conserve glycogen, for the steady state portions of you long efforts so you will have something in the tank when you need to spring. It is quite possible that this study, if it is right, has little bearing on endurance athletes like ultra runners or Ironmen, but it would be a game changer for folks doing 100+ mile bike races ;-).

FWIW, I think we are all doing this through training already. By the nature of the way we train, we do already train our bodies to get at our stored fat more easily. At best, I suspect this study, even if it is on to something, is just an extra 1% over what we are all already doing with our bodies as part of our training i.e. changing the ratio of our energy sources towards fat.

They could have used the same amount of muscle glycogen but burned less liver glycogen than the high carb athletes. Possibly.

The original article is freely available.
http://www.sciencedirect.com/science/article/pii/S0026049515003340


They don't comment on that aspect other than to say it is interesting.

Full study here:

http://www.metabolismjournal.com/...334-0/fulltext#s0010


Funded by Quest nutrition and Atkins foundation.

The other issue is that they were 4 hours fasted pre V02 test, but each group had a shake right before the three hour test, LC group had a high fat shake HC group had a high carb shake.

Resting RER values were in the range of .72 for LC and .86 (+-.08) for HC…basically .86 is about IM bike effort…while resting???

Maurice

I was going to make a comment about this needing to be in pink, but it's for real!

so u need carb to perform? go figure #sarcasm

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The entire event (IM) is like "death by 1000 cuts" and the best race is minimizing all those cuts and losing less blood than the other guy. - Dev

Never has so much been studied, written and debated on a subject that has so little to do with performance on race day.

We have ample access to nutrition in 99.99% of all races. We aren't chasing Gazelles across the the Serengeti Desert.

Who the crap cares what % of carbs vs fat vs glycogen you are using as fuel....

Keep the gels and sport drink flowing and it's all good!!

my 02 cents..

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"Good genes are not a requirement, just the obsession to beat ones brains out daily"...the Griz

Except when it's not. I've done everything from half marathon's up to IM's using both approaches. My results have been remarkably consistent. However, the experiences have been significantly more unpleasant for me in the gut region when relying on gels and sports drinks. Since eliminating or drastically reducing their use, I have not had to stomach issues.

I am not in research, I understand though that these studies can be quite expensive…to me it raises issues, but perhaps to those who have a better understanding of funding, on the surface it may raise serious red flags…or may not be an issue at all.

The one thing is not being in a fasted state for the extended test and then having different "shakes" for both the LC and HC group. I don't see any value in the data for the three hour test.

Maurice

It is also in peer review now.

Regardless of the funding source, doesn't passing peer review lend legitimacy?

I'll let others in research comment on that. It is quite a grey area, and above my pay grade ;-)

Regardless, it doesn't mean that laymen can't or are unable to comment on the legitimacy or relative value of the test(s) being conducted. IE why the unfasted state in the 3 hour test? Why the different substrate fuel sources pre test for different groups? Why at rest does the HC group have substrate utilization equal to 70-80% (or more) of FTP?

EDIT: also looks like blood lactate is spiking in the LC group vs stable in the HC group, I wonder what would happen at 6-9-12 hours vs 3?

Maurice

I think the point is that many people think low-carb is desirable for reasons other than bolstering athletic performance, but some fear that this will have a negative impact on athletic performance and recovery, for which glycogen is clearly key. And this article suggests that that mechanism isn't present, so one major reason not to pursue low-carb if you're an athlete doesn't find empirical support here.

There's not a direct performance advantage to utilizing more fat and less glycogen, and for some people there's zero benefit, but some people get an indirect performance improvement. Athletes who struggle with correcting GI issues that force them to slow down can benefit when they're able to consume less during races, allowing them to maintain pace. It's not going to make someone faster who isn't limited by GI problems.

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____________________________________________
Don Larkin
Reach For More
http://www.reachformore.fit/
USAT Lvl1 Coach, NSCA-CPT, NASM-CPT, BS Exercise Science

Spoke with undergrad's today about this paper....

1) Individuals highly adapted to LCHF diet showed hight fat use during steady state endurance exercise vs. HCLF elite athletes.

2) Great so substrate use reflects adaptation, not an unreasonable point.

But, IMHO, the glaring flaw and also slightly disingenuous use of certain words like elite is the implication LCHF is better for you as elite athlete and this is just wrong. It is well documented that in order TO GO FAST YOU NEED CARB's ... FACT.


If the study had carried out, instead of steady state, a 3hr Time Trial run as fast as possible I guarantee the findings would be wholly different.

So try not to overlook this when trying to maximise your performance vs. use more fat when "going steady".

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David T-D
http://www.tilburydavis.com

Just like a bunch of pro-carb research comes out of the Gatorade Institute. Or that the study finding chocolate milk was a good recovery drink was funding by the Dairy Council. It seems people overlook those facts because it supports the mainstream beliefs.

Whilst we can always debate implicit conflicts of interest I would offer that ultimately it is the research methods that should be scrutinised....were there enough subjects to draw valid conclusions? Were the statistical analyses appropriate? Was it a very simple study or was it a meta analysis?

There's plenty of ways to valid or tear holes in science before questioning the funding. Because ultimately all research is funded in some way, researchers lose their jobs if they are not bringing in sufficient grants.

Just because their is a correlation between the funding party and the research it does not always mean that it is the causation of the findings.

Regards

David

p.s. No I don't work in research.

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David T-D
http://www.tilburydavis.com

I would think any sports drink company would be "pro-carb." It was one of their scientists that first figured out that combing sources of carbohydrates led to quicker/better absorption. We certainly see that utilized in some of the more popular endurance products right now. While I can't say that I enjoy regular Gatorade during endurance events, they have a lot of legitimate researchers on staff and have done some cool work. The release of Gatorade Endurance and their big(ger) electrolyte profile came awfully close after the Campbells funded hydration/re-hydration research that showed chicken noodle soup and chicken broth beat the heck out of Gatorade. It is possible that industry sponsored research can improve the general landscape of competing/related products.


There's more than one study looking at chocolate milk. They weren't all funded by the National Dairy Council.


The source of funding doesn't dictate the results. It dictates whether or not it actually gets researched. It's not like NIH funding has been expanding... Let's not pretend like the above-mentioned projects are multi-site studies where the data is only seen by the sponsors and their (on their payroll) statisticians.