But I'll give you a link on this matter (note: this is a one time thing, just so people can see that everytime I have been saying somehing my information was correct and subsequently that of Tim was wrong)
Also the not so geeky guys might like this. It is easy readable and written by Layne Norton:
Acute hormone fluctuations are largely irrelevant in the bigger picture in my opinion. It takes chronic superphysiological doses in order to have significant effects.
Although GH increases protein synthesis, it is not in skeletal muscle (Yarasheski et all, 1992). GH has some influence on lipolysis, but this effect is very small and only occurs when insulin is low, therefore you would lose the benefical effect of insulin on protein degradation. Furthermore, fasting results in increased AMPK and decreased mTOR, inhibiting protein synthesis.
I agree with you that GH has influence on lipolysis, but if you try to stimulate GH by fasting, you lose the bigger picture: fasting has a negative influence on protein synthesis for example.
Effects of GH in human muscle and fat.Quote
Jorgensen JO, Rubeck KZ, Nielsen TS, Clasen BF, Vendelboe M, Hafstrom TK, Madsen M, Lund S
Pediatr Nephrol. 2009 Nov 10;
Just to back this up:Originally Posted by jornT
Impact of fasting on growth hormone signaling and action in muscle and fat.Quote
Moller L, Dalman L, Norrelund H, Billestrup N, Frystyk J, Moller N, Jorgensen JO
J Clin Endocrinol Metab. 2009 Mar ; 94(3): 965-72
GH isn't a very potent enhancer of skeletal muscle protein synthesis, though it is pretty potent in fat metabolism. GH's effects are exerted mainly through IGF-1 as alluded to, but there are both hepatic and local IGF-1. The latter accounts for only 25% of total IGF-1 but is responsible for the skeletal growth, while the former being involved in fat/cho metabolism.
One thing GH does in acute action is increase sensitivity to catecholamines, even in absence of any direct lipolytic action. Further, I don't agree that GH is really lipolytic only in the absence of insulin. Cortisol has been shown to attenuate lipolysis and stimulate LPL in the presence of insulin, while GH inhibits it. (Ottosson et al 2000). Endogenous GH release during exercise is also in fact an independent predictor of fat oxidation while epinephrine was not (Gibney, 2007.... this is an excellent paper).
Still a little ways to go Jorn :gaysign:
1. Effects of Cortisol and Growth Hormone on Lipolysis in Human Adipose Tissue. The Journal of Clinical Endocrinology & Metabolism Vol. 85, No. 2 799-803
2. The Growth Hormone/Insulin-Like Growth Factor-I Axis in Exercise and Sport. Endocrine Reviews 28 (6): 603-624
However GH may be more more potent than I thought on fat metabolism based on a quick peak at your other reference. I will look into that, but I can already add that GH release is one of the MANY responses to fasting and you have to take them all into account. Again, look at the bigger picture.