View Full Version : 40 Hour Fast and Skeletal Muscle Genes

Peter Borden
06-01-2007, 07:29 AM
I'm new to this forum but have been following various forms of IF on and off for a long time. I didn't see this study mentioned here, it suggests that at least 40 hours of fasting can be done without muscle loss.

Ann Nutr Metab. 2006;50(5):476-81. Epub 2006 Aug 24.

Actions of short-term fasting on human skeletal muscle myogenic and atrogenic gene expression.

Larsen AE, Tunstall RJ, Carey KA, Nicholas G, Kambadur R, Crowe TC, Cameron-Smith D.

School of Exercise and Nutrition Sciences, Deakin University, Burwood, Vic, Australia.

BACKGROUND: Skeletal muscle mass is governed by multiple IGF-1-sensitive positive regulators of muscle-specific protein synthesis (myogenic regulatory factors which includes myoD, myogenin and Myf5) and negative regulators, including the atrogenic proteins myostatin, atrogin-1 and muscle ring finger 1 (MuRF-1). The coordinated control of these myogenic and atrogenic factors in human skeletal muscle following short-term fasting is currently unknown. METHOD: Healthy adults (n = 6, age 27.6 years) undertook a 40-hour fast. Skeletal muscle biopsy (vastus lateralis) and venous blood samples were taken 3, 15 and 40 h into the fast after an initial standard high-carbohydrate meal. Gene expression of the myogenic regulator factors (myoD, myogenin and Myf5) and the atrogenic factors (myostatin, atrogin-1 and MuRF-1) were determined by real-time PCR analysis. Plasma myostatin and IGF-1 were determined by ELISA. RESULTS: There were no significant alterations in either the positive or negative regulators of muscle mass at either 15 or 40 h, when compared to gene expression measured 3 h after a meal. Similarly, plasma myostatin and IGF-1 were also unaltered at these times. CONCLUSIONS: Unlike previous observations in catabolic and cachexic diseased states, short-term fasting (40 h) fails to elicit marked alteration of the genes regulating both muscle-specific protein synthesis or atrophy. Greater periods of fasting may be required to initiate coordinated inhibition of myogenic and atrogenic gene expression.

Ron Nelson
06-01-2007, 08:27 AM
My only question is why would anyone want to fast for 40 hours?
19 seems like an eternity some days. Doubling it, without a really good excuse, seems like futility.

Brad Hirakawa
06-01-2007, 09:19 AM
Often, the questions asked/answered in a scientific paper do not directly relate to real-world conditions.

They may have gone with a time-point used in a previous article, or perhaps that was as long as the subjects could hold out before they got real cranky. Or, they actually measured longer time-points, did see deterioration and whacky changes in gene expression.. but are saving that for their next publication. :)

Edit: My question: who would be crazy enough to volunteer for a 40 hours fast followed by a procedure that involves a large-bore needle punched into the thigh... ick

Brad Hirakawa
06-01-2007, 09:24 AM
And.. welcome aboard Peter and thank you for the article. Full text would be nice.. if you can get it. :)

Robb Wolf
06-01-2007, 09:36 AM
Welcome and fantastic post!

Scott Kustes
06-01-2007, 09:49 AM
Edit: My question: who would be crazy enough to volunteer for a 40 hours fast followed by a procedure that involves a large-bore needle punched into the thigh... ick
College students.