Fasting And Muscle Mass

Yesterday's post on Fasting grew a few questions and comments among readers so I decided to investigate and go deeper on the topic. In short the first question was about fasting and muscle mass gains. If someone's trying to get a bigger build wouldn't fasting dampen the chances of growing?

Andrew talked about his experiences with intermittent fasting:

I experimented with it for a while. there is a lot of different protocols but i was looking at 

lean gains which is 16 hr fast with an 8 hr feeding window. its nice because you can eat bigger

meals as long as they are during the time, but its tough. i would do skip breakfast, do cardio,

then eat my first meal around noon. usually save the carbs postworkout and only eat

protein/fats before. its not bad, some people have trouble training with no carbs or on little food 

but its not bad once you get used to it. i think its more about meal timing and the body's responses rather 

than losing weight via not eating for 16 hrs. i liked it okay, lost some weight, not much strength loss.

If you search online that's what most of the testimonies will say also. If you read yesterday's post you probably remember the study conducted on the mice. One day they fasted the next they pigged out and this process repeated. The fasting mice were actually healthier, leaner, and lived longer than non fasting mice even though double calories were consumed on non fasting days. However, as an athlete your training may be dampened by a lack of glycogen stores. In theory a lack of amino acids may also decrease the bodies ability for protein synthesis. So what do we do?

Athletic Fasting:

One research article suggest's that when someone works out in a fasted state and then consumes a high carbohydrate high protein high leucine drink post workout they actually stimulate a greater intramyocellular anabolic response[1]. The drink ratio was 50% carbohydrate, 33% protein, and 17% leucine at 6g drink per kg bodyweight. So someone who weighs 198 lbs [or 90 kg] would consume a 540 ml solution comprised of 270 g carbs, 178 g protein, and 92 g leucine. These numbers sound really high and almost impractical so this research study can be considered unique to circumstances.

In another study we see that when someone is in a fasted state they are more IGF-1 and Insulin sensitive and therefore are more impacted by these hormones [2]. Therefore when you exercise fasted and then consume carbohydrates mixed with protein you're actually allowing your muscles to be more sensitive towards growth. A question that pops up in my head is that intermittent fasting may also help with diabetes II, more to come on this topic I hope.

In a study conducted in mice the evaluation of muscle turnover, protein synthesis, was observed during a fast. The two groups of mice were lean, and obese. The lean mice had increased protein synthesis for a short period during the fast, mainly because they only lasted 10 days. The obese mice, who lasted 60 days, had longer bouts of increased protein synthesis even though the metabolism rate was the same as the lean mice.[3] This suggests that fasting can lead to increased protein synthesis in mammals, which we are, as long as it's not taken too far.


Fasting will result in lower glycogen levels and can reduce someones ability to perform athletically. Therefore for an athlete the suggested fasting protocol would be to fast until one hour before practice and then consume a carbohydrate dense meal. For example practice is at 3 p.m. so the athlete will wake up and carry on their day and then consume a meal at 2 p.m. This will make the gap between their last meal and this one, assuming they ate at 9 p.m. the night before, 17 hours. If someone is just training for fitness then training while fasted can support greater protein synthesis theoretically. In the end it comes down to your desires and will power

  1. Louise DeldicqueKatrien De BockMichael MarisMonique RamaekersHenri NielensMarc Francaux, Peter Hespel (2010) Increased p70s6k phosphorylation during intake of a protein–carbohydrate drink following resistance exercise in the fasted state. Retrieved  Volume 108, Number 4 (2010), 791-800DOI: 10.1007/s00421-009-1289-x
  2. Bang PBrismar KRosenfeld RGHall K.(1994) Fasting affects serum insulin-like growth factors (IGFs) and IGF-binding proteins differently in patients with noninsulin-dependent diabetes mellitus versus healthy nonobese and obese subjects. retrieved  J Clin Endocrinol Metab. 1994 Apr;78(4):960-7.
  3. MICHAEL A. DUNN,3 SHARYN K. HOUTZ ANDE. W. HARTSOOK4 (1982) Effects of Fasting on Muscle Protein Turnover, the Composition of Weight Loss, and Energy Balance of Obese and Nonobese Zucker Rats'. retrieved Nutrition Laboratories, Department of Dairy and AnimalScience, The Pennsylvania State University, University Park, PA 16802


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About Me

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BS, MS - exercise Physiology
EPC - Board Certified Exercise Physiologist

Published Thesis
The impact of three different forms of warm up on performance

The Effects of Glucose Supplementation on Barbell Velocity and Fatiguability in Weightlifting - A pilot study"

The Accute Effects Of Different Squat Intensities on Vertical Jump Performances
The Accute Effects of Different Squat Intensities On Jump Performance

Graduate from Midwestern State University, founder of Endunamoo Barbell Club, and Endunamoo Strength and Conditioning. Working to help athletes physically reach their goals and achieve scholarships while spiritually pouring into as many people as possible on all platforms.