Fung versus Phinney on Long Term Fasting and BMR

(Bob M) #1

In the last 2 Keto Dudes episode with Dr. Phinney, he states that “study after study” on longer term fasting shows decreases in basal metabolic rate (BMR). Yet, here’s a page from The Complete Guide to Fasting, showing the exact opposite:

. BMR.pdf (474.6 KB)

This is obviously a study of longer-term fasting and apparently refutes Dr. Phinney’s assertion.

As someone who has done over 5 fasts of 4.5-5. days, and is about to try another 4.5 day fast next week, I’d like to know: am I lowering my BMR or not?

(Omar) #2

Both are respectful and trustworthy doctors

But I wish I know the answer

#3

Any study done on sugar-burners will show likely a drop in BMR (because in fact the body can’t fully access its own fat, so it makes sense that it would down-regulate metabolism), so unless the subjects were fat-adapted, there’s really not much to see there.

And in any case I suspect that - in the absence of chronic calorie restriction or high insulin - our BMR may actually turn out to be one of those things that’s relatively fluid. Eat more for a few weeks? your metabolism goes up. Cut back for a while and it probably drops a bit. Kind of makes sense, and it reflects other changes that are seen in fasting. Organs shrink during fasts, which sounds terrifying until you see (in Longo’s studies) that after the refeeding they return to their normal size (presumably with healthier cells).

I would think it would only be a problem if it’s chronic restriction that puts the body into some kind of a famine state.

#4

I would think that if you are properly feasting between fasts, your BMR will not be significantly affected over time.

(Joanna Parszyk ) #5

I was about to say the same Rachelg :wink:
Also it depends how much fat storage a person has, if any exercise (which is muscle sparing) is applied.
My advice is not to fall into a routine so that body gets used to something too much. Mix it up, change routines and the best way to make sure that your BMR stays high is to have a proper fatty keto feast after a fast.