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Old 01-26-2006, 01:22 PM   #1
John Vivian
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Got in a little over my head in a discussion on another board about optimal nutrition and i am hoping that someone can set me straight.

One of the items discussed was the efficiency of the metabolism of carbs vs. fats for energy in the face of depleted ATP and muscle glycogen.

The statement was made that, "Fat metabloism is not as efficient as carbohydrate metabolism. Muscles fueled with carbohydrate perform better than muscles fueled with fat because aerobic fat metabolism consumes more O2 per unit of ATP produced than does aerobic carbohydrate metabolism. Provided that fuel is not limited, oxygen delivery and consumption are rate limiting. Because aerobic carbohydrate metabolism consumes less oxygen than aerobic fat metabolism, a carbohydrate burning muscle will perform at a higher level than a fat burning muscle... All of the studies I could find comparing high fat to low fat diets in endurance athletes focused on exercise done at around 60% VO2 max. This is fat metabolism territory. If you work harder, ie in the 80 to 90% VO2 max area you need carbohydrate metabolism to provide the energy".

The discussion started with the benefits (or lack thereof) of rice for nutrition and quickly grew to a general discussion of carbs vs. fat for fuel.

Now, i'm not looking for ammo for an argument, just clarification for my own benefit; i have already conceided that this goes well beyond any knowledge i have.

If you're interested, the thread is here:

http://www.mma.tv/TUF/index.cfm?ac=L...6&FID=24&pc=40


Any help is appreciated.

john
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Old 01-26-2006, 02:36 PM   #2
Robert Wolf
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John-

The fat adapted athlete will use, on average more fat for fuel at levels below the lactate threshold and at rest. For a variety of reasons that is good.

The difference between a mediocre and good endurance athlete is their ability to use fat at ever higher energy outputs. less lactate production and longer time to gylcogen depletion and "bonking".

The Zone offers a nice ballance here as it provides sufficient carbs for intensity but forces an adaptation towards fat metabolism. This is also the diet used by Randy Couture which is recomended by Dr. Phil Maffetone.

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Old 01-26-2006, 02:47 PM   #3
John Vivian
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Thanks, Robb.

That certainly supports the use of the Zone for athletic endeavors.

Are the comments made about the efficiencies of fat vs. carb utilization for energy correct? Perhaps a better question would be, are they relevant in light of your second statement?

What happens once the glycogen stores are depleted and the athlete continues to work (completing a marathon, for example)? In this case what would the best source of energy be, and what is the most efficient means of supplying it?

Sorry if you answered this and i missed your point.

Thanks again,

john
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Old 01-27-2006, 02:05 AM   #4
Paul Kayley
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Hi Rob, long time no speak, hope you're well!
John, I have tried all diets going for optimal performance as an endurance athlete. Rob is spot on with his advice above. I have found that it is important to become tuned into and more aware of how your individual physiology/metabolism responds to various quantities of each macronutrient, with a specific diffentiation between fructose based, and starch based carbohydrates. Its also important to learn how to periodise your nutrition in balance with the periodised emphasis of your training.

Rather than focus purely on one or the other, its good to train the muscles to run well off both fats and carbs together. The rate restriction of fat oxidation is only an issue at higher intensities, and is relative to genetic aerobic potential and conditioning. The glycolytic system is without doubt faster than the lipolytic system, however its very duration limited. The fat/carb issue is also only a small part of the physiological puzzle in this respect. Suffice to say its best to train both energy pathways to maximum potential.

Use The Zone as a central nutritional hub throughout the training year, protein being a constant. Then vary fat intake and carb type and quantity in balance with your body's need for each. Fat should also be balanced in respect to desired body composition - if weight lose is required create a negative fat balance, and vice versa. Only target starches for muscle glycogen replenishment (preferably at the end of the day's training) when they are becoming close to empty, ergo following long or hard workouts, and immediately after exercise when bloodflow to the depleted muscles is optimal. At other times target natural sources of fructose to replenish liver glycogen and allow the body to naturally regulate blood sugars.

I personally find the zone too complicated to run to the letter, albeit in principle very sound. The Paleo Diet for Athletes is very clever, but my favorite eating system is an adapted Warrior style diet....

Its not what you eat, but when you eat and what you've been doing, that makes what you eat matter.
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Old 01-27-2006, 03:44 AM   #5
Randy Roper
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Paul, can you explain what this means: "if weight lose is required create a negative fat balance, and vice versa."
Randy
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Old 01-27-2006, 05:48 AM   #6
Paul Kayley
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Consume less fats than you oxidise for energy - probably a slight over-simplification, but it works providing the body has access to bodyfats (via low insulin and elevated catecholamines).
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Old 01-27-2006, 07:10 AM   #7
Greg Battaglia
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I think this is the most interesting topic. Some say carbs are absolutely neccesay for intense exercise. I disagree. I follow a pretty low carb diet (15-20% of total calories) with fats composing the majority of calories (about 65%) and I notice that my performance is better when I stick to this ratio. When I move more towards Zone ratio's my performance goes in the toilet. It's interesting to note that although more reasearch is needed, some suggest that IMT's (intra muscular triglycerides) are a superior fuel to glycogen. It's also worth noting that fat provides nearly double the amount of ATP as carbohydrates. I would listen to Robb and Paul because it seems like I'm an exception to the rule around here.
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Old 01-27-2006, 07:19 AM   #8
John Vivian
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Paul, thanks for your feedback. i typically wait about an hour after working out before i eat anything, and then it is typically a Zone / Paleo meal. The reason for waiting is to allow Growth Hormone to do it's work (i believe this approximates Art DeVany's pattern and rational). i also do not do any sort of carb loading and just eat balanced meals all of the time. i think you are suggesting that a post-workout carb load might be appropriate. What are your thoughts / rational on this?

Thanks very much,

john

(Message edited by atomic_dog on January 27, 2006)
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Old 01-27-2006, 07:22 AM   #9
John Vivian
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Greg, i also have a diet fairly high in fat. My protein and carbs are in Zone balance and i am eating about 6x fat. This works out to 20% protein, 25% carbs, and 55% fat. Likewise, i have also found that my performance is better than before i was following a Zone diet.

john
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Old 01-27-2006, 08:45 AM   #10
Greg Battaglia
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John, our diets seem extremely similar. I also wait about and hour before eating anything. I feel like it gives my body time to slow down after an intense WOD. Food right after doesn't seem appetizing to me. Anyway, I wouldn't do the post workout carb load for the reason that you already don't. It'll lower GH and increase insulin; NOT GOOD. Some swear by carb loading but I was never a big fan. It usually puts weight (fat) on me and makes me feel tired and lethargic. Maybe try it and see, but I'd say it's unneccassary and maybe even counter productive.
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