Phinney found no performance degradation from very low carb as long as  
you give it enough time. Here's what he says about the time for  
adaptation:
"There are to date no studies that carefully examine the optimum  
length of this keto-adapatation period, but it is clearly longer than  
one week and likely well advanced within 3–4 weeks. The process does  
not appear to happen any faster in highly trained athletes than in  
overweight or untrained individuals. This adaptation process also  
appears to require consistent adherence to carbohydrate restriction,  
as people who intermittently consume carbohydrates while attempting a  
ketogenic diet report subjectively reduced exercise tolerance."

Stephen D Phinney, Ketogenic diets and physical performance, Nutr  
Metab (Lond). 2004; 1: 2.

Note that he also called for adequate sodium, potassium (and I would  
atgue for magnesium) nutriture as well as moderate protein intake to  
prevent gluconeogenesis.

Jim Swayze
www.fireholecanyon.com
Sent from my iPhone

On Aug 26, 2009, at 3:26 PM, "Day, Wally" <[log in to unmask]> wrote:

>>> How long have you given zero carb time to adapt in the past?
>
> Boy, I think the longest is 2, maybe 2-1/2  weeks. I inevitably gave  
> up because 2 weeks is long enough to put up with "hitting the wall".
>
> I have no trouble adjusting to "low" carb (say, 50-100g per day). I  
> do my morning ride to work on an empty stomach and have no energy  
> loss whatsoever. But when I do meat/fat only for a couple days I  
> start getting this rubbery legs feeling and general loss of endurance.
>
> Funny thing - I experienced the exact same symptoms when I (long  
> ago) experimented with natural hygiene and vegetarianism. I guess  
> I'm just a born omnivore.