LCHF impaires performance

ianrobo · 2016-12-25 16:48:29 UTC

On twitter a couple of anti LCHF’ers quite excited by this abstract

ncbi.nlm.nih.gov

Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers.

LM Burke, ML Ross, LA Garvican-Lewis, M Welvaert, IA Heikura, SG Forbes, JG Mirtschin, LE Cato, N Strobel, AP Sharma and JA Hawley, The Journal of physiology, 2017 05 01

Three weeks of intensified training and mild energy deficit in elite race walkers increases peak aerobic capacity independent of dietary support. Adaptation to a ketogenic low carbohydrate, high fat (LCHF) diet markedly increases rates of whole-body fat oxidation during exercise in race walkers over a range of exercise intensities. The increased rates of fat oxidation result in reduced economy (increased oxygen demand for a given speed) at velocities that translate to real-life race performance in elite race walkers. In contrast to training with diets providing chronic or periodised high carbohydrate availability, adaptation to an LCHF diet impairs performance in elite endurance athletes despite a significant improvement in peak aerobic capacity.We investigated the effects of adaptation to a ketogenic low carbohydrate (CHO), high fat diet (LCHF) during 3 weeks of intensified training on metabolism and performance of world-class endurance athletes. We controlled three isoenergetic diets in elite race walkers: high CHO availability (g kg-1 day-1 : 8.6 CHO, 2.1 protein, 1.2 fat) consumed before, during and after training (HCHO, n = 9); identical macronutrient intake, periodised within or between days to alternate between low and high CHO availability (PCHO, n = 10); LCHF (< 50 g day-1 CHO; 78% energy as fat; 2.1 g kg-1 day-1 protein; LCHF, n = 10). Post-intervention, V̇O2 peak during race walking increased in all groups (P < 0.001, 90% CI: 2.55, 5.20%). LCHF was associated with markedly increased rates of whole-body fat oxidation, attaining peak rates of 1.57 ± 0.32 g min-1 during 2 h of walking at ∼80% V̇O2 peak . However, LCHF also increased the oxygen (O2 ) cost of race walking at velocities relevant to real-life race performance: O2 uptake (expressed as a percentage of new V̇O2 peak ) at a speed approximating 20 km race pace was reduced in HCHO and PCHO (90% CI: -7.047, -2.55 and -5.18, -0.86, respectively), but was maintained at pre-intervention levels in LCHF. HCHO and PCHO groups improved times for 10 km race walk: 6.6% (90% CI: 4.1, 9.1%) and 5.3% (3.4, 7.2%), with no improvement (-1.6% (-8.5, 5.3%)) for the LCHF group. In contrast to training with diets providing chronic or periodised high-CHO availability, and despite a significant improvement in V̇O2 peak , adaptation to the topical LCHF diet negated performance benefits in elite endurance athletes, in part due to reduced exercise economy.

however on reading it I am confused did these athletes Keto adapt or in fact are we seeing a report that just confirms what we all knew during keto adaption ?

robomgwtf · 2016-12-25 16:27:16 UTC

Unfortunately there are 2 important things to know.

Louise who conducted test is very much anti-fat
It takes more than 21 days to b fat adapted, most take between 3-6mths .

Oh and the amount of carbs for a serious performance athlete was quite low. Those who are keto adapted use more carbs … Can be 150-200g and still b in state of ketosis. The key is taking the time to get to that point.

ianrobo · 2016-12-25 16:29:24 UTC

Which goes to another debate on he sports section. So in fact all this study did was to prove something everyone knew anyway !

robomgwtf · 2016-12-25 16:34:17 UTC

Yep. A waist of time, money.
The carbers all saying carb timing crucial.
Well duhhhhhh…
In any endurance event, lchf athletes still use carbs but only when they have to which is of course towards the end for a final burst, not every 30-45mins otherwise.

ianrobo · 2016-12-25 16:40:28 UTC

Yep but it is amazing how the carber docs etc jump onto anything ! How could anyone think that they could make it pass ?

richard · 2016-12-25 16:47:47 UTC

I suspect it is desperation, after several years where the science is apparently not going their way even slightly.

ianrobo · 2016-12-25 16:49:25 UTC

I note @richard a lot for Aus institute of sport so given the position of Dr Bruckner is this the motivation ?

richard · 2016-12-25 16:52:09 UTC

I think he’s got his own domain he is allowed free reign within as long as the team is getting results.

ianrobo · 2016-12-25 16:59:29 UTC

and no one denies he got that despite some dodgy results … not due to fitness at all