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Should I eat fat or carbs? Or both?

Posted March 05, 2015 07:59PM by Skye in the Running Forum

Skye
Skye Skye Nott
@TheStaminist   Skye Nott Staminist.com
Location: Vancouver, Canada
Joined: 2 years ago   Posts: 495

Looks like fat is getting a reprieve from the "it will kill you" category. Even the NYT is getting on the ketogenic diet bandwagon:

http://well.blogs.nytimes.com/2015/02/25/should-athletes-eat-fat-or-carbs/

And this PubMed article: Rethinking fat as a fuel for endurance exercise

"A key element contributing to deteriorating exercise capacity during physically demanding sport appears to be reduced carbohydrate availability coupled with an inability to effectively utilize alternative lipid fuel sources. Paradoxically, cognitive and physical decline associated with glycogen depletion occurs in the presence of an over-abundance of fuel stored as body fat that the athlete is apparently unable to access effectively. Current fuelling tactics that emphasize high-carbohydrate intakes before and during exercise inhibit fat utilization. The most efficient approach to accelerate the body's ability to oxidize fat is to lower dietary carbohydrate intake to a level that results in nutritional ketosis (i.e., circulating ketone levels >0.5 mmol/L) while increasing fat intake for a period of several weeks. The coordinated set of metabolic adaptations that ensures proper interorgan fuel supply in the face of low-carbohydrate availability is referred to as keto-adaptation. Beyond simply providing a stable source of fuel for the brain, the major circulating ketone body, beta-hydroxybutyrate, has recently been shown to act as a signalling molecule capable of altering gene expression, eliciting complementary effects of keto-adaptation that could extend human physical and mental performance beyond current expectation. In this paper, we review these new findings and propose that the shift to fatty acids and ketones as primary fuels when dietary carbohydrate is restricted could be of benefit for some athletes."

The thing I'd be concerned about is the reduction in "metabolic flexibility" by having only having access to one fuel source.

It seems like if you're relying on ketones, then all of your efforts have to be aerobic? Doesn't anaerobic activity rely on glycogen stores?

Skye

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slee Paul Sly
  Paul Sly
Location: Vancouver, Canada
Joined: 2 years ago   Posts: 14

Quote
Skye


The thing I'd be concerned about is the reduction in "metabolic flexibility" by having only having access to one fuel source.

It seems like if you're relying on ketones, then all of your efforts have to be aerobic? Doesn't anaerobic activity rely on glycogen stores?

Skye


Here is some information (for one person) regarding a ketogenic diet, metabolic flexibility, and lactate threshold:

http://eatingacademy.com/how-a-low-carb-diet-affected-my-athletic-performance

A good primer on eating a ketogenic diet and exercise is "The Art and Science of Low Carbohydrate Performance", by Phinney and Volek:

http://www.artandscienceoflowcarb.com/the-art-and-science-of-low-carbohydrate-performance/

Their research shows that when muscles burn fat for fuel, there is less lactic acid created, which leads to a higher lactate threshold.

Skye
Skye Skye Nott
@TheStaminist   Skye Nott Staminist.com
Location: Vancouver, Canada
Joined: 2 years ago   Posts: 495

Interesting, thanks! I'll read up on that later today.

Here's some interesting research about lactic acid accumulation:

http://staminist.com/read.php?1,5

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