Fasting and amino acids

(Erin Macfarland ) #1

I am wondering about the science behind whether taking a BCAA supplement or other amino acids “breaks” a fast? So, for example, I like to do a daily fast of about 16 to 18 hours, and I like to work out fasted in the morning. However, I find a get a boost of energy and in performance if I do some BCAA’s or full spectrum amino acids beforehand. Is this halting the fast and preventing the benefits such as autophagy from taking place? I am really lean and my performance flags sometimes because I don’t have much body fat to draw energy from. But I would hate for these supplements to impact the fasting benefits.


My “gut” reaction is that BCAAs would break both the decreased insulin and autophagy associated with a fast, but have no science to support it, so I’ll be monitoring this thread closely since I would also like to know.

(Erin Macfarland ) #3

I know fat does not disrupt the fast, but since BCAAs are a type of protein, which does disrupt the fast to a degree, I’m wondering how they compare to actually ingesting meat or animal protein. I take about 3 g along with some Keto cana, and exogenous ketone, and I can power through a tough workout without taking in any food beforehand. I consider it to be a semi fasted state since I do take in some calories from the ketone supplement. But I feel like there are still benefits to engaging in a workout with these additions.


My understanding is that amino acids (BCAA’s, and in particular leucine) cause a release of insulin.

(Richard Morris) #5

The BCAA leucine is the amino acid most inhibitory of autophagy. So it could shut down one of the processes you are trying to engage by fasting.

(Erin Macfarland ) #6

Bingo!! I wonder if it’s an issue of scale. My bcaa supplement has 2.5 g of leucine. Can that really disrupt the autophagy process and cause an insulin response?

(Richard Morris) #7

I don’t know how much would be needed and for how long autophagy would be inhibited.

(Erin Macfarland ) #8

That report is incredibly dense…I can’t sort through the language!

(Erin Macfarland ) #9

Doing some research there are opposing views on this subject, and I think there are definitely some exceptions that affect whether the bcaas have a negative effect on fasting. Some feedback supports the idea that the small amount of amino acids in a low dose do not affect the process of fasting in a significantly detrimental way. Others say they will cause an insulin spike but do not specify at what dose this occurs. If you are very lean, you risk muscle loss during a fasted workout is the thought. Would I be able to detect an insulin response to the aminos by measuring my BG after ingesting them?


This isn’t an answer to your question, but you might find it interesting.

I am currently listening to Ben Greenfield’s podcast episode from Jan 18, 2017. He is talking to Dominic D’Agostino and it is titled Which Ketone Supplement Works Best.

At ~33 minutes in, they are discussing BCAA’s and fasting.

At the beginning of the podcast, he does suggest getting your Propeller Hat on for the nerdiness. hahahaha

(Erin Macfarland ) #11

That is hilarious…I posted a link to that episode in “Show me the science”. It was excellent


oops! :grinning: I’m sorry I haven’t been on as much as usual the last few days. I am way far behind…64 new topics I haven’t even looked at!

(Erin Macfarland ) #13

Hey great minds think alike! :wink: