Carb deficit and cycling

[yello]

Following on from another thread that touched on carbohydrate deficit and endurance sports, I let google be my friend and came up with some rather interesting reading...

...a study entitled Ketogenic diets and physical performance.

(A 'ketogenic' diet, btw, is basically no carbohydrate. Think perpetual bonk!)

Its interesting reading alone for the cultural and historical backdrop it paints (the Inuit naturally no-carb diet, the rise of the carb in our diets, etc) but the meat of it (ho ho) is in the science.

I'll cut to the chase; the study suggests that a no carb diet is possible for an endurance athlete. Basically, the body goes through an adaptation stage of 1 to 2 weeks whilst it adjusts (during which time a drop in performance will be seen) but after that, once the body has learnt to fuel itself from non-carb sources, performance returns.

Personally, I wouldn't try it as I like my cake too much BUT I'm hoping you might find it an interesting read! In all seriousness, I would welcome comments.

 

[iLB]

this would be useful for short term weight loss (burning fat), but unsustainable in the long term i would have thought.

 

[Crackle]

Fossilised evidence shows that early hunter-gatherers managed.

 

[yello]

The thing is (or seems to be) it IS sustainable in the long term. The Inuits seemed to manage it!

 

[ASC1951]

The Inuits seemed to manage it!

So what? They also had little choice. What's the point, when our success as a species comes from being omnivores?

 

[GrasB]

Fossilised evidence shows that early hunter-gatherers managed.

Me liky!

 

[yello]

So what? They also had little choice. What's the point, when our success as a species comes from being omnivores?

With all due respect, I think you've missed the point. It's not about choice, species success or herbivore/carnivore/omnivore distinctions. The point is that people can happily exist and function normally on a (virtually) no-carb diet.

 

[Dan B]

As a matter of interest, what's the inuit life expectancy?

 

[yello]

I don't know and the study does not say. Nothing to stop you following that up if though should you be interested in the answer.

Whatever the answer might be, you'd have to ensure the figure didn't include non-diet related deaths (which I assume is your point) and other differentiating factors. For instance, I know suicide is purported to be high in very northern regions. Now they could all be topping themselves because they're sick of fish and whale blubber but I don't think so!

Note that the study does not look at the suitability of an Inuit diet for physical performance, merely a low carb diet. The two are not the same. So let's not get too sidetracked by the thought of fish suppers... and lunches... and breakfasts.... for the rest of all time.

 

[ASC1951]

With all due respect, I think you've missed the point.

With even greater respect, you asked for comments. That was mine.

As onmivores, we can live on all sorts of diets. That doesn't mean a restricted diet is sensible or desirable. The study in your link is in large part a report of an experiment conducted by a couple of people 80 years ago based on what they though the traditional Inuit diet was 50 years before that. His modern lab test was a small scale short trial on fixed equipment.

Even then, his conclusion is simply -

Both observational and prospectively designed studies support the conclusion that submaximal endurance performance can be sustained despite the virtual exclusion of carbohydrate from the human diet.

- in English "You can sustain effort with a carbohydrate-free diet, but you don't do as well as if it did contain carbohydrate." I'm glad I wasn't funding his project.

 

[yello]

With even greater respect, you asked for comments. That was mine.

As was mine... this could run and run But I am glad it's teased more out of you. Seriously.

That doesn't mean a restricted diet is sensible or desirable.

I'd agree. That's a personal choice in many respects. The study only suggests it is possible, and that is what interested me.

The study in your link is in large part a report of an experiment conducted by a couple of people 80 years ago based on what they though the traditional Inuit diet was 50 years before that. His modern lab test was a small scale short trial on fixed equipment.

I go further. I'd say the historical aspect laid out is anecdotal and can't really be used as the basis for a conclusion. The lab test is, despite it's short term nature, interesting; the observation of a drop in performance and a recovery. I'd agree, it'd be interesting to see how the cyclists performed over a longer time frame.

Even then, his conclusion is simply - - in English "You can sustain effort with a carbohydrate-free diet, but you don't do as well as if it did contain carbohydrate."

I think the latter bold bit is you're own interpretation. In fairness, I don't think the study concludes that. The study does add caveats about it not simply being a carb restricted diet but careful attention to other factors is also required. Note that the report also concludes...

Therapeutic use of ketogenic diets should not require constraint of most forms of physical labor or recreational activity, with the one caveat that anaerobic (ie, weight lifting or sprint) performance is limited by the low muscle glycogen levels induced by a ketogenic diet, and this would strongly discourage its use under most conditions of competitive athletics.

Note the context, "therapeutic use", AND the direct advice regarding such diets and anaerobic performance.

Let me lay out some back story here. I was taken by a claim I read that there was no dietary requirement for carbohydrate to sustain life. Given that we, as cyclists, are given info about carbo loading and are sold energy bars, drinks and gels etc etc etc, I was interested as to how cycling (or any level of activity generally) featured in a 'sustained life'.

Jimbo, of this very forum, has addressed this point specifically. He has, in the past, posted quite detailed info on how he calculates his carb requirement for particular expenditures of effort. Whether he factors in a base level daily requirement, I can't remember.

But this study seems to indicate that, indeed and as I had read, that there is no base level requirement and one can (if so desired) perform "most forms of... recreational activity" on a low carb diet.

I have already stated that I personally would not do it, nor would I necessarily recommend anyone else to, but it is interesting none-the-less that seemingly it can be done, and safely. I don't know specifically what "therapeutic" reasons one might have (something perhaps to do with controlling blood sugars, diabetes like things, etc) but that's neither here nor there.

 

[Fiona N]

I'm not surprised that a carb-free (or at least very low/seasonal) diet will maintain life or even that it's possible to undertake endurance-type activities while existing on such, my question is - why would you?

Other extreme diets (I mean this in the scientific sense not as a way of loosing weight) such as veganism or even raw vegansim (not entirely sure what the tachnical term for this is) at least have a rationale even if you don't agree with it. Whereas no-carbs diets seem to me to be hankering after some illusory 'golden age' when humans lived off meat and fish alone. You only have to read the studies of diets of nomadic, hunter-gatherer tribes in less cold climates to realise carbs and, particularly sugar (e.g. honey), are an integral and sought after part of the diet. The Inuit have had to adapt as they, for most of the year, don't have the choice but look at how enthusiastic they are about any sort of fruit in the summer.

So why push your body to something it will only do at a push?

 

[yello]

Whereas no-carbs diets seem to me to be hankering after some illusory 'golden age' when humans lived off meat and fish alone.

I wouldn't agree entirely with that. It's probably true to say that some advocates of the diet believe that (and the 'primitive diet' argument does have some persuasive arguments imho, so - yes - I personally would say such diets have an arguable "rationale") but I'm equally sure there are other reasons why someone might want a no-carb diet. What they might be, I don't know but the "why" of it doesn't actually bother me. Suffice to say, I wouldn't class it as deluded even though I wouldn't personally do it.

I'm going to read further on this, especially the "at a push" aspect you refer to. I really would like to know just how adaptable our systems are and what, if anything, is compromised. Intuition (or previous teachings, call it what you will) tells me carb is essential. The study would suggest otherwise. I like it when I get these knowledge clashes!

 

[e-rider]

I'm at the end of my first week of a low carb diet and my performance has dropped on the bike.

 

[Soltydog]

About 2 years ago I went on a very low carb diet, on the advice of my doctor.
Performance was affected My 16 mile commute time went up by 10-15% I didn't feel as energetic, but had more get up & go Lost about 2 stone in 3 months tho
I avoided carbs for about 6 months before slowly re-introducing them into my diet, but I still dont go mad fuelling up on carbs, not even for long rides & manage ok