I am really excited about today’s episode of the podcast. Episode 471, which airs today, is clearing up some major nutrition misconceptions and misunderstandings.
Most of them came up in response to episode 469 on extended fasting.
We’ll tackle a bunch of them, but I want to dive into one specific one right here on the blog.
If you’d rather listen to this blog than read it, please click play. Otherwise, keep reading below.
In episode 469 I explained that your body won’t burn your muscle tissue for fuel when you’re fasting, so long as you have a body fat percentage over (approximately) 4-6%.
Someone responded with a disagreement. Her stance is that science PROVES you lose lean mass because some research has shown an increase in urea in the urine during fasting compared to non-fasting.
To get everyone on the same page, urea is a byproduct of protein metabolism. This listener, and some researchers, conclude that protein metabolites in the urine during fasting (when you aren’t consuming protein), prove that your body burns lean muscle during a fast.
WRONG.
It doesn’t prove that. Here’s why:
Metabolizing protein does not mean burning muscle tissue. Understand that lean muscle tissue is NOT the only protein component in your body. Not even close. Could burning lean mass produce an increase of urea in the urine? Yes of course. But that doesn’t mean that increased urea in the urine means you’re burning lean mass.
There are many other (more) logical explanations.
For example: we talked about autophagy, right? In both episodes 469 and 470 we talked about this cellular clean up process where your cells, under certain conditions, are able to eliminate broken, defective or old components.
Guess what? Some of those components (perhaps many of those components) are proteins. So, as we go through this cellular detoxification and clean-up, we will see metabolites of that process in the urine.
If you have questions or rebuttals to this, make sure you listen to episode 471 first because we’ll go more deeply into this issue and many more including:
- Why urine ketones might not reflect if you’re in ketosis or not
- Why you can’t judge a fast exclusively by what happens during a fast (you must consider what happens after the fast)
- What fuels your muscles during a workout when muscle glycogen has been exhausted?
Have other questions or looking for clarification? Let me know and we’ll dive into them here on the blog or on the podcast!
Make it a great day!
I love your podcasts! Having a background in science research and medicine, I love the science-geeky stuff the most! I’m a relatively new listener (lurking in the background for about 5-6 weeks), but had to subscribe because each podcast has consistently provided fresh and solid information.
Awesome! Thanks so much for listening!!
Jason Fung did a bit of a study and he concluded that for some people yes they did lose muscle on an extended fast however they gained it back quickly. I just can’t remember all the details. IF I recall properly the benefits for his patients in their obesity health concerns that was a small sacrifice for them to make to get them out of danger since they were not sticking to a proper diet so fasting was easier to implement (his book also mentions this point which is often lost on a lot of people on the reason he implemented fasting for his patients in the first place). I also heard another interview of Jason Fung more recently that made me start to question fasting lengths for healthy people who are maintaining their weight. The studies are not conclusive and are not enough of them to really prove if there is really a health benefit with respect to autophagy like we think it is. When I find that interview I will email it to you as I think it is worth the listen. I have done a 3 day fast which worked out great. I also did a 5 day fast with you and Ella last year. My personal experience was not as good on 5 days – true no hunger but I dropped temperature too low and I didn’t feel any benefit other than I could tell it messed me up with my metabolism and eating afterward HOWEVER I am only 113 lbs so perhaps it was too lengthy for me personally. I am still learning :-). Anyway I am not disagreeing with anything I just find the fasting rather interesting and enjoy learning about it as time goes on and more studies are done.