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View Full Version : Glucose vs. Fatty Acids as Muscle Fuel



threatmix
01-22-2006, 10:04 PM
Is there merit to this statement:


Fatty acids are transported into the mitochondria as completely intact molecules. Glucose, on the other hand, can be transported only after it has been broken down first into pyruvate by the process of glycolysis . This is then used anaerobically to produce energy with lactate as a by-product.

The by-products of the energy-production process when fatty acids are used are carbon dioxide and water, both of which are easily excreted. But when glucose is used, the lactic acid produced in the conversion process can build up in muscle cells and make them ache.


?

ddegroff
01-22-2006, 10:19 PM
Glycolysis is a long chain reactions to form ATP. This process is used to make energy for your body while working out. Yes, the by-product of this reaction is lactic acid. Glycolysis does have by products that are all re-used for more reactions down the road.

So yes there's merit for part of this statement. But a little lactic acid isn't going to hurt you.


Edit: H2O is also a by product of Glycolysis.

threatmix
01-22-2006, 10:45 PM
Okay. And what about the fatty acid part? By the way, the context of this statement is an article that claims fat is a better energy source for the body than carbohydrates. It references some studies, but it looks questionable (which is why I'm questioning it).

ddegroff
01-23-2006, 10:30 AM
Can you post the article or tell me where to find it. I'm interested in reading it. Also let me look around for the fatty acid answer and get back to you.

Holto
01-23-2006, 10:42 AM
Fat is the ultimate energy source. I remeber Web talking about eating huge cheseburgers and having legendary workouts.

It makes sense especially around training.

Anthony
01-23-2006, 10:46 AM
A lot of performance athletes would agree that fat > carbs for efficient energy.

threatmix
01-23-2006, 10:58 AM
Here's the article:

http://www.second-opinions.co.uk/athletic_diet.html#N_5_

This guy is an archer (yeah...) who has a few references for the article.

ddegroff
01-23-2006, 11:10 AM
Of course fat is a great energy source (9 k/cals per gram) where as carbs are only 4 k/cals per gram. The only thing you have to watch out for while eat that much fat is your intake of saturated fat. Thats really not hard to do if your paying attention to the types your eating. As far as which method of metabolism is better than the other, I feel there isn't much difference.

TheGimp
01-23-2006, 01:11 PM
By the way, the context of this statement is an article that claims fat is a better energy source for the body than carbohydrates

Bear in mind that fats are more easily digested than (complex) carbohydrates. Very roughly 10% of carbohydrate calories are expended digesting them, compared to 5% of fat calories.

Spartan936
01-23-2006, 01:49 PM
I have been very interested in this topic for some time. So if fats truly are a better and more efficient source for energy, then what does that mean in terms of diet? Are we talking about a high fat diet? 40% calories from fat? 50%? Gimp? Anthony? Holto?

I have noticed that my workouts just plain suck when I don't have some fat in me. I swear, nutrition is one giant contradiction.

Built
01-23-2006, 01:55 PM
I usually suggest 0.5g/lb LBM for fat consumption, rather than think of it as a percentage of total calories**. That way you get enough fat even when you're cutting.

And you do need SOME saturated fat.



**Reference: Dorgan J, et al. Effects of dietary fat and fiber on plasma and urine androgens and estrogens in men: a controlled feeding study. Am J Clin Nutr 64(6): 850-855. 1996.

Spartan936
01-23-2006, 02:00 PM
Thanks built, But what about bulking on thousands of calories? .5 g/lb LBM gives me very few calories. I guess I'm asking how much fat can be in the diet, and how beneficial it would be on energy levels. I have type 2 diabetes, needless to say, I'm a little tired of carbohydrate madness, lol.

TheGimp
01-23-2006, 02:09 PM
Thanks built, But what about bulking on thousands of calories? .5 g/lb LBM gives me very few calories. I guess I'm asking how much fat can be in the diet, and how beneficial it would be on energy levels. I have type 2 diabetes, needless to say, I'm a little tired of carbohydrate madness, lol.

I would guess it's a case of experiment and see what works best for you. I find it easier to fill up my daily calories with carbs, once I've factored in 1g/lb of bodyweight in protein and adequate fats but others may struggle with carbs this high with spiking blood sugar making it hard to control appetite for instance. Equally I'd imagine that high fats, with their satiety, may make it harder to eat more.

Spartan936
01-23-2006, 02:14 PM
Sounds good to me gimp. I think I'll be slowly adding large amounts of olive oil into my diet, lol. Hopefully it will stabilize my energy. I have no problem making shakes (with the oil) and downing them until I get enough calories, and I feel all pukey.

Wow, I just invented a word. Pukey.

I wonder how many athletes really utilize higher fat diets?

Utopianhopes
01-23-2006, 02:23 PM
It takes energy (calories) to build muscle. During training and muscle building, carbohydrate is the preferred fuel. If you don't eat enough carbs, your body may break down your protein (including muscle tissue) for energy. So eat a little protein along with lots of carbohydrate foods to power the muscle 'construction'.

When you are trying to gain muscle mass, about 1.7 g protein / kg body weight (roughly twice the normal/average requirement) is adequate for meeting the extra needs for building muscle. For an 80 Kg person, 1.7 g protein / kg body weight is about 136 grams of protein. You can consume that much protein by eating a variety of meat, poultry, fish, legumes, milk and grains every day as part of a balanced diet.

Extra protein (over and above 1.7 g/kg body weight) is used as energy or stored as fat. The best strategy is to eat protein foods with your carbohydrate based meals to ensure that you have adequate building material as well as enough energy to fuel your workout and muscular growth.

Resistance training is essential to stimulate muscular growth. The small amount of carbohydrate (glycogen) that is stored in muscle is used as energy during a workout. These stores need to be replenished after exercise, and eating carb foods like grains, legumes, fruit, vegetables, milk and yogurt will refill the glycogen stores for your next exercise bout. A post workout meal high in protein and low in carbs might satisfy your hunger, but will leave glycogen stores on low, resulting in a lack lustre workout the next time at the gym. Have you ever tried to train when your whole body felt like lead? This may be the feeling of low glycogen stores. Fatigue, inability to focus, headaches and dizziness are signals of low blood sugar. If you avoid carbs, you may notice these symptoms before, during or after a workout.

I am confused on why fat is better?....

Source (http://www.forces.gc.ca/health/services/health_promotion/Engraph/quiz_e.asp)

Vapour Trails
01-23-2006, 04:02 PM
Is there merit to this statement:



?

Lactate is only formed when oxygen is low. When oxygen is low or nil, cellular respiration stops and hence fat oxidation (because oxygen is the final electron acceptor). I don't really understand the point of the argument you originally posted. During an intense set, your body has no choice but to form lactate. But as soon as you catch your breath, lactate is converted back to pyruvate and it will enter the respiratory chain.

It should really read like this:

"Fatty acids are transported into the mitochondria as completely intact molecules. Glucose, on the other hand, can be transported only after it has been broken down first into pyruvate by the process of glycolysis . This is then used anaerobically to produce energy with lactate as a by-product, but only when oxygen is limited. ".

The by-products of the energy-production process when fatty acids are used are carbon dioxide and water, both of which are easily excreted. But when glucose is used, the lactic acid produced in the conversion process can build up in muscle cells and make them ache. Yes, but if lactate is building up, fat oxidation is impossible, because obviously oxygen is limited.

Built
01-23-2006, 05:58 PM
Thanks built, But what about bulking on thousands of calories? .5 g/lb LBM gives me very few calories. I guess I'm asking how much fat can be in the diet, and how beneficial it would be on energy levels. I have type 2 diabetes, needless to say, I'm a little tired of carbohydrate madness, lol.

0.5g/lb LBM for fat is a minimum. I usually go closer to about a gram per pound LBM on a bulk. Basically, I use fat as a caloric ballast.

threatmix
01-23-2006, 08:54 PM
Yes, but if lactate is building up, fat oxidation is impossible, because obviously oxygen is limited.

Fat oxidation does not require the presence of oxygen (in the form of O2). And why can lactic acid fermentation only occur in the absence of oxygen?

ddegroff
01-23-2006, 11:01 PM
It has to do with the way it is broken down. If no O2 is present the the pyruvic acid turns to lactic acid, if oxygen is present the the pyruvic acid go to the citric acid cycle which goes to form ATP. When no O2 is present you get 2 ATP and 2 Lactic acid molecules, the reason for LA production is to save it for later when O2 is avaible.

threatmix
01-24-2006, 08:12 AM
Right. But the point is, fatty acids can be oxidized even without oxygen, and with no by-product of lactic acid.

ddegroff
01-24-2006, 09:57 AM
Correct but once oxygen is avaible our body turns the lactic acid into glucose. Then our body turns it into ATP.

Holto
01-25-2006, 09:32 AM
ddegroff
threatmix
Vapour Trails

Good Posting. You guys need avatars.