Growth hormones and fasting

#1

Hey guys, I have a question about what happens with growth hormones during fasting. Forgive me if this has been covered in previous topics, I couldn’t find the answer to my specific question.

I know on 2 Keto Dudes and from what Dr. Fung says that HGH and IGF are measurably increased during fasting, and that this is a good thing. But I have also seen sources (like Mosley’s documentary “Eat, Fast, and Live Longer”) where they measure IGF and see it going down during fasting. They say this is good too, that lower IGF levels are beneficial. I’m trying to figure out if they are talking about the same thing or different processes entirely, since the claims seem contradictory. Help me out?

Thanks!

(Todd Allen) #2

Fasting lowers insulin our storage hormone and increases growth hormone which mobilizes energy substrates, raising both glucose and free fatty acids. Growth hormone enables the release of growth factors such as IGF-1. But IGF-1 which stimulates protein synthesis, in particular muscle protein, also depends on essential amino acid availability such as methionine and leucine. In a fasted state the availability of these amino acids is low suppressing IGF-1.

Low IGF-1 contributes to degenerative conditions such as sarcopenia and osteopenia while high IGF-1 accelerates cancer. There is debate about what the ideal range is and the degree it should swing up/down over various time frames. I suspect our disconnect from natural rhythms, daily and seasonal contributes to our problems at each end of the growth spectrum.

#3

Also fasting stimulates autophagy which causes the body to repurpose old protein since it needs protein. Supposedly after the fast is over this stimulates the body to create new protein from the scavaged cells to replace the old protein.

It is confusing and I think the question is excellent

#4

Also @brownfat

Thank you both for your explanations! These forums are awesome. Everything you say makes sense. I was watching that documentary with Michael Mosley and that’s where my confusion started. He talks to Valter Longo, who asserts that fasting decreases IGF. Everyone involved appears to support fasting, but it confused me to hear him say that fasting increases longevity by decreasing IGF. I get the feeling from what you’re saying that it’s a complicated process so maybe these assertions aren’t contradictory so much as oversimplified for the purpose of the documentary.

(Todd Allen) #5

Yes, the clearance of damaged proteins, dysfunctional organelles and senescent cells through autophagy is a hot area of research and looks to be one of the important benefits of fasting. However the amino acids liberated through this recycling process are supporting ongoing needs of repair, regeneration and especially gluconeogenesis to sustain a minimal blood sugar level. Refeeding after the fast provides new protein that supports regrowth.

(Bacon is a many-splendoured thing) #6

You might want to check out some of Ron Rosedale’s videos on insulin, IGF, and mTOR. I’m not entirely sure he’s right (Benjamin Bikman says essentially opposite things, and he sounds equally convincing), but it’s worth checking out anyway.