2

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Yet another Ketosis question...

Answered on August 19, 2014
Created August 03, 2011 at 3:16 AM

How long till it registers?

100fd85230060e754fc13394eee6d6f1

(18706)

on August 03, 2011
at 03:26 PM

In fact, some people have made the absurd claim that the reason ketosis gives a "metabolic advantage" is that ketones are wasted in the urine, and that once you adapt it is no longer an advantage. Therefore, they conclude, it is better to prevent adaptation by going in and out of ketosis. This explanation makes that strategy seem counter-productive.

100fd85230060e754fc13394eee6d6f1

(18706)

on August 03, 2011
at 03:23 PM

The explanation I've heard in the past about long-time VLC'ers spilling fewer ketones is that they "adapt" to using them better, and don't waste them so much, but I never thought that made much sense.

100fd85230060e754fc13394eee6d6f1

(18706)

on August 03, 2011
at 03:20 PM

Great reference, Rose. It also explains why there is a difference between being in ketosis and being keto-adapted, a point I haven't fully appreciated before. I've often heard that full adaptation takes weeks, and didn't know what the adaptation consisted of, and how it differed from that point at which ketones appear in the urine.

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3 Answers

7
3aea514b680d01bfd7573d74517946a7

(11996)

on August 03, 2011
at 04:27 AM

From Phinney and Volek's (excellent) new book, The Art and Science of Low-Carbohydrate Living:

Within a few days of starting on carbohydrate restriction, most people begin excreting ketones in their urine. This occurs before serum [blood] ketones have risen to their stable adapted level because un-adapted renal tubules actively secrete beta-hyroxybutyrate and acetoacetate [two forms of ketones] into the urine. This is the same pathway that clears other organic acids like uric acid, vitamin C, and penicillin from the serum.

Meanwhile the body is undergoing a complex set of adaptations in ketone metabolism. Beta-hydroxybutyrate and acetoacetate are made in the liver in about equal proportions, and both are initially promptly oxidized by muscle. But over a matter of weeks, the muscles stop using these ketones for fuel. Instead, muscle cells take up acetoacetate, reduce it to beta-hydroxybutyrate, and return it back into the circulation. Thus after a few weeks, the major form in the circulation is beta-hydroxybutryate, which also happens to be the ketone preferred by the brain cells (as an aside, the strips that test for ketones in the urine detect the presence of acetoacetate, not beta-hydroxybutyrate).

[...]

These temporal changes in how the kidneys handle ketones make urine ketone testing a rather uncertain if not undependable way of monitoring dietary response/adherance. Testing serum for beta-hydroxybutyrate is much more accurate, but requires drawing blood, and it is expensive because it is not a routine test that doctors normally order.

A non-invasive alternative is to measure breath acetone concentration. [...] A number of businesses have developed prototype handheld devices to measure breath acetone, but at the time of this writing, nothing practical is on the market.

This is interesting to me, as I didn't know that most of the ketones circulating in a keto-adapted person like myself are beta-hydroxybutyrate and not acetoacetate. This helps explain why in many long-term VLCers the strips stop turning dark -- it isn't just that they're "spilling" few ketones, it's that they don't have as much of the acetoacetate, which the strips measure, floating around in their blood, and therefore excreting in the urine.

100fd85230060e754fc13394eee6d6f1

(18706)

on August 03, 2011
at 03:23 PM

The explanation I've heard in the past about long-time VLC'ers spilling fewer ketones is that they "adapt" to using them better, and don't waste them so much, but I never thought that made much sense.

100fd85230060e754fc13394eee6d6f1

(18706)

on August 03, 2011
at 03:20 PM

Great reference, Rose. It also explains why there is a difference between being in ketosis and being keto-adapted, a point I haven't fully appreciated before. I've often heard that full adaptation takes weeks, and didn't know what the adaptation consisted of, and how it differed from that point at which ketones appear in the urine.

100fd85230060e754fc13394eee6d6f1

(18706)

on August 03, 2011
at 03:26 PM

In fact, some people have made the absurd claim that the reason ketosis gives a "metabolic advantage" is that ketones are wasted in the urine, and that once you adapt it is no longer an advantage. Therefore, they conclude, it is better to prevent adaptation by going in and out of ketosis. This explanation makes that strategy seem counter-productive.

3
B14dc4aa1ddefbec3bc09550428ee493

on August 03, 2011
at 03:59 AM

It usually takes me about three days to really feel it.

2
1568416ef28477d1fa29046218d83ddd

(6235)

on August 03, 2011
at 03:41 AM

Depends on your body you can get the test strips, but for me it is pretty obvious because my urine changes smell dramatically. For me it can vary between 12 and 48ish hours depending on what I have been eating and how active I have been.

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