I study anatomy and physiology and my lecturer said that people usually go into a state of gluconeogenesis (conversion of amino acids and fats to carbs) in around 6-10 hours without eating. This state is brought on after the liver has run out of glycogen. Now if im not correct Mark Sisson, Brad pilon and Martin Berhkan all state that muscle wont be lost during a fast and that it is conserved by raised levels growth hormone. But if gluconeogensis occurs, does'nt that mean that GH is not doing its job as the IF advocates and Sisson state? Would we be losing muscle in a fast?
This is a great topic. Lets put it in simple terms.
If gluconeogenes occurs, protein will be converted to glucose. This is a guarantee.
In the absence of dietary protein, or in this instance, a completely fasted state, amino acids from muscle will be the source.
Therefore, if this occurs, which it will, muscle will be lost in some capacity.
All of those guys you mentioned have great information and I greatly respect all of them. In practical terms, they are ALL correct. For most functional people and for the practicality of what we are able to measure visually or even tangibly, the muscle mass loss is NOT going to be significant enough for someone to notice it by looking in the mirror. Many of these same people who use fasting, are also re-feeding adequately after a fast, involved in other activities which stimulate and build new muscle tissue and therefore, over a period of time, will still see a net gain.
The best way I can think of it is counting from 0 to 100. Instead of going straight to 100, you go back 1 number for every 10 you reach. Eventually, you still get to 100 and over the long-term, you really never notice the difference in the trend from 0 to 100. I guess if you were able to take constant measurements of lean mass (this is impossible to do without any counteracting margin of error anyway) you may be able to notice the difference.
Your liver doesn't have to be depleted of glycogen as a precursos to gluconeogenesis, neither do you have to eat an excess of protein (although both of those things will certainly induce it).
Gluconeogenesis is a natural part of your body's metabolism, and almost everyone utilises it every day. Dr Richard Feinman says this of gluconeogenesis on a "regular" diet: "It is true that your brain needs glucose, but glucose can be supplied by the process of gluconeogenesis; that is, glucose can be made from other things, notably protein. This is a normal process: when you wake up in the morning, between thirty and seventy percent of your blood glucose comes from gluconeogenesis." http://www.diabeteshealth.com/read/2008/12/25/5383/low-carbohydrate-diets-why-you-dont-want-the-experts-to-tell-you-what-to-eat/
So we're all engaged in gluconeogenesis every day, if we eat a high protein diet or not.
I believe gluconeogenesis is always occurring, it's just the amount of its contribution that may change. Lactate is also a major substrate for it. Also, some of the output goes to refill liver glycogen, and in that case it is referred to as glyconeogenesis.
Doubt Martin or his followers are losing muscle. Besides, most of those IFers are using BCAA during the fast. Also consider Hard exercise can induce gluconeogensis. That's why post work out meals are highly anabolic. Muscle breaks down. you feed it properly. it'll adapt for size or strength
A little detail which some people are forgetting here: gluconeogenesis can have both substract from muscle aminoacids pool OR available aminoacids. The latter is the prefered if adequate amounts of protein are beeing delivered. The former is rather to occur if the latter are not present.
So, gluconeogenesis may mean the metabolic transaltion of lactate or amino acids for energy purposes,but not necessarly from muscle tissues.
What I am confused about is if after a bout of fasted exercise if you then have a high protein meal what happens is your insulin raises slightly while glucagon soars to keep blood sugar high because there is little or no carbs in your meal. Beacuase of this glucogenesis needs to continue and therefore more of your muscle must be being wasted?
Also with low insulin levels due to lack of carbs how do the nutrients and what not get absorbed into your muscles to help with regrowth & repair???
Or am I being a fool and am missing something?? Any insights would be great!! :) Thanks, Dax
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