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Discussion Starter · #1 ·
I read the paleo diet and found a chapter on restocking muscle fat and glycogen stores. For example the day before race, I should load up on carbs to fill my muscles with fat and glyco- the energy I'll use during the race. But what I REALLY want to know, is when does the muscle stocking stop, and the fat storage start? I can't imagine stocking up on carbs everyday before I do my ride will be a good thing. I think I'd store fat. So how does it work?
 

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Please read a book that is based in science. You cannot load fat or use fat as a primary energy source during a race. There are many books that include a scientific approach to carbo loading or weight loss, if thats what you're worried about.
 

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Call me a Fred
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Fat is the primary energy source during exercise.
 

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Discussion Starter · #5 ·
Your'e a coach and you've never heard of intramuscular fat? This is fat that is stored in the muscles. When you exercise you burn a combination of fat and sugars from foods. The harder you move, the more you use simple sugars as fuel from glycogen stores and whatever is digested from your gut. But fat is always floating around in your blood as well.
 

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Discussion Starter · #6 ·
kbiker3111 said:
Please read a book that is based in science. You cannot load fat or use fat as a primary energy source during a race. There are many books that include a scientific approach to carbo loading or weight loss, if thats what you're worried about.
Book: "The Paleo Diet for Athletes" by Loren Cordain PhD and Joe Friel, MS. If you know any better experts than these two on the science of diet I'd like to know who they are. I never said fat was the primary source of energy. Glyocogen is. And fat is used in combination as well. My question was, when does carb loading stop, and fat storage start.
 

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flankwood said:
I read the paleo diet and found a chapter on restocking muscle fat and glycogen stores. For example the day before race, I should load up on carbs to fill my muscles with fat and glyco- the energy I'll use during the race. But what I REALLY want to know, is when does the muscle stocking stop, and the fat storage start? I can't imagine stocking up on carbs everyday before I do my ride will be a good thing. I think I'd store fat. So how does it work?
I don't know for sure, but I doubt they are entirely independent processes. I don't know the physiology of how carbs get converted into to fat but I suspect that as long as liver and muscle glycogen levels are depleted the vast majority of carbs go there to be stored as glycogen. I would think still some will be being converted to fat in adipose cells, maybe muscle or liver cells, can't recall ever reading anything about it?

I've never read anything about there being a concern for replacing intramuscular fat stores for exercise, I assume because glycogen depletion/replacement is the weak link in the chain so fat depletion is never an issue.
 

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iliveonnitro said:
What the hell is muscle fat? That's an oxymoron...
There's actually two stores of muscle fat. Intermuscular (i.e. between the cells). If you look at the muscles of obese people vs. normal weight with imaging techniques you can see the greater amount of fat in the obese muscle. Or you can just go buy a steak to see it, a good cut generally is well-marbled, that is, it has a lot of intermuscular fat. Wild game meat is almost always from extremely lean animals and so the meat is very tough as it doesn't have much fat in it.

There is also intramuscular fat stored within the muscle cells. One of the adaptations to endurance training is to store more fat in the muscle cells than a sedentary person. Interestingly people who develope type 2 diabetes also appear to have excess fat stored in their muscle cells and this is thought to impair the insulin signaling cascade and perhaps ultimately be the cause of the diabetes. Obviously in endurance athletes this doesn't happen. The theory is that we continuously deplete and replace our intramuscular fat whereas in an obese sedentary person the fat just sits there and somehow becomes "toxic" causing the diabetes.

The fat for energy when you start exercising generally comes from the blood, either released by the intermuscular fat stores or remote adipose tissue, as the duration of the exercise increases you tend to switch from the fat delivered via the blood and rely more on the intramuscular fat stored within the muscle cells themselves.
 

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isn't the goal of carb loading to increase glycogen stores in muscle/liver rather than effect fat storage? I can't imagine that the availability of fuel from fat is ever a limiting factor for even a highly trained athlete, so even someone like a Rasmussen with extremely low fat stores doesn't run out of fuel from fat. Isn't the limiting factor glycogen, particularly since racing typically involves intensities that require over 80% of energy from glycogen?

I've read that it's possible to increase glycogen stores to around 160g in the liver and 720g in the muscle via various loading procedures. Carmichael describes one in his nutrition book that can be done the day before an event, so it doesn't interfere with training leading up to the event.
 

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stevesbike said:
isn't the goal of carb loading to increase glycogen stores in muscle/liver rather than effect fat storage? I can't imagine that the availability of fuel from fat is ever a limiting factor for even a highly trained athlete, so even someone like a Rasmussen with extremely low fat stores doesn't run out of fuel from fat. Isn't the limiting factor glycogen, particularly since racing typically involves intensities that require over 80% of energy from glycogen?
Yes, that's why no one worries about fat depletion.
 

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Short and long term

flankwood said:
I read the paleo diet and found a chapter on restocking muscle fat and glycogen stores. For example the day before race, I should load up on carbs to fill my muscles with fat and glyco- the energy I'll use during the race. But what I REALLY want to know, is when does the muscle stocking stop, and the fat storage start? I can't imagine stocking up on carbs everyday before I do my ride will be a good thing. I think I'd store fat. So how does it work?
While there is a fair amount of variation between people, the best way to think of it is that fat storage is a response to a (relatively) long term excess of carbs in your system. IOW, you don't get fat storage this afternoon from that Big Gulp soda you had at lunch, but if you keep your carb stores high day after day, the excess carbs will be converted to fat.

The way it works is that if you take in more calories than you expend, you will store fat. If your calorie intake matches your expenditure, your fat stores will remain constant. If you take in fewer calories than you expend, your fat stores will decline. For those who don't want to think too hard about it:

Eat more = gain weight. Eat less = lose weight.
 

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flankwood said:
Book: "The Paleo Diet for Athletes" by Loren Cordain PhD and Joe Friel, MS. If you know any better experts than these two on the science of diet I'd like to know who they are. I never said fat was the primary source of energy. Glyocogen is. And fat is used in combination as well. My question was, when does carb loading stop, and fat storage start.
I've never read the Paleo Diet for Athletes, so for all I know it may be the greatest volume on nutritional advice we will ever come across. I do know the Paleo Diet was borderline rubbish and Loren Cordain often contridicts his own research in that book. I also know that Joel Friel (god that he is) has always had a weakness in nutrition. His different versions of the Bible have often included nutritional advice that at best can be called common wisdom. For nutritional advice I would pick up any physiology textbook, read research by guys like Asker Jeukendrup, cautiously read what Monique Ryan puts out and read the first and last thirds of Dave Morris' book.

As far as carbo loading the day before riding, I wouldn't worry about it. Carbo loading is mildly unpleasant and only good for that extra one or two percent. Eat a well balanced diet and you should be ok for most of your riding. The rare occasion that you really load up on carbs for an event won't affect your fat levels much b/c you should more than burn it off in said event. FYI, there is a difference between carbo loading and eating a diet with plenty of carbs. If you're cycling a lot you shouldn't be doing any of that high protein stuff.

Obviously, this doesn't answer your original question, where does carb storage end and fat storage begin. I don't know. I do know that the body can't load up on carbs quickly, so its something that needs to be done progressively over a few days; adding less than 100g of carbs/day to your diet should be plenty for a carbo load.
 
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