Hi all,
I've been using ketostix daily since Jan 1st. They have been very accurate, based on the previous day's carb and exercise. I pretty much know whether or not to see trace, moderate or large (or none, if I ate my carbs later and overindulged a bit )
So, I was looking at products, and I read that if you have sustained ketosis, eventually the ketones don't show up in your urine anymore, and to detect them you need to get some kind of keto breath analyzer.
I don't understand how that would be biologically reasonable - the ketones should still be in your urine, but maybe ALSO in your breath if you've maintained ketosis over time.
Has anyone else ever seen an elimination of ketones in the urine, but had them present in your breath?
Thanks,
Tracy

Urine ketones are regulated by the kidneys, they can increase the fraction of ketones that are reabsorbed, this is what is upregulated when blood ketones are high but urine ketones are low. Since the lungs don't have such a mechanism, the relation of breath ketones to blood ketones should stay more stable over time.

Is it true that once you are fully "keto adapted" (aaand, I don't actually know wha that means...) that the stx are no longer useful becasue you can be efficiently and exclusively burning body fat for energy, but the ketones no longer show in your urine?

Jamackarch - I have NOT found that to be the case, and I have been honestly low-carbing since January 1st. I don't know if maybe it works after, say, a year, but for 5 full months the keto sticks still reflect what I think is an accurate ketone level (based on what I ate the day prior). I was thinking of investing in the breath ketone-detector, but as of now see no reason for it I hope this helps!

That sort of depends. Early on, brain and muscle both will use fair amounts of ketone for energy. With fasting, ketoadaptation actually involves muscle adapting to free fatty acids to a greater extent for energy, this spares ketones and glucose for the brain. With nutritional ketosis, this switch away from glucose/ketone metabolism for muscle could spare both--with less competition for the bit of glucose the body produces even on a ketogenic diet, this could make for a decreased demand for ketone production.

If you look at it, actual brain demand for energy is about what you'd get from 100 grams of glucose.

For a person eating a moderate 100 grams of protein, in theory you could get two thirds as much glucose through gluconeogenesis, but call it fifty, expecting things to be that efficient is probably a bit much.

Add 20 grams of glucose from a fairly strict level of carbohydrate restriction. We're up to 70 grams of glucose.

Call daily metabolism 2000 calories per day, whether the rest of the calories are made up from body or dietary fat, and assuming protein is in balance. That's about 169 grams of fat as triglyceride. About ten percent of that triglyceride is glycerol, so there's 17 grams or so of glycerol available to produce a similar mass of glucose. We're up to 87 grams of glucose, at least potentially, so you can see that depending on just how efficient the body can become at sparing glucose for the brain, it's not entirely surprising if not everybody is throwing off much in the way of ketones even if they're on what looks like a fairly ketogenic diet. Two people could be eating the same exact diet, burning the same calories, on in ketosis, the other not--but both burning just as much fat.

teaser - you have a MUCH more robust understanding of body chemistry than I! Thank you very much for your replies - they are very enlightening.

I'm using a ketonix breath tool and experimenting. So far so good. I'm going to do some fasting and see if the strips compare numbers on the electronic device. I'm recording this all on our daily weigh-in thread http://forum.lowcarber.org/showthread.php?t=473253

Here's all of the data I've collected so far on the device:
http://downhaul.com/lowcarb/ketonix/ketonixMay23.png

And the chart that converts their "number" to acetone PPM. I'm shooting for 55 plus during the fasting right now I"m running under that and there is no indication on the strips I have:
http://downhaul.com/lowcarb/ketonix/ketonixScale.png

I don't take this stuff too seriously and am having fun with it. Its interesting as hell - who knows what the body does!

I'm into month 4 of ketosis, and I'm assuming I'm still there since I'm eating the same food, under 20 carbs, and fasting 20 hours 3 days a week (I've lost 33 pounds). The ketostix have turned pale and pink, and I've decided to just stop using them. I believe this is why people turn to the blood or breath analyzers -- I'm not sure I'll go in that direction as they are expensive.

Short on time but I have some interesting data to post later, well at least I think it's interesting. I've been side by side comparing ketonix breath thing and strips for a few months. Have notices some recent changes!

edit, this will have to wait till this evening or tomorrow but for now I can post some things I'm tracking...

Here's a chart/scale to decode the ketonix readings:


Here's my daily logs from as far back as logging them on thread.

http://downhaul.com/lowcarb/daily.txt

The most recent ones include the ketonix device (KX) and KP for "Ketones in Pee" readings from strips. Strips are in mg/dL I belive, Ketonix are mmol/L after you do the look up I think. I'm shooting for the number on the meter to show between 55 and 70 or so. I think this is about the range I've heard called "optimal"

here's the new daily weigh-in thread where I track. I've cut back on net carbs and things are getting more interesting.

http://forum.lowcarber.org/showthre...232#post9128232

I have not done the math yet to see if the mg/dL on the stick and mmol/L on the ketonix device are similar.

Another new wrinkle is that I ditched diuretics a little over a week ago. Weight went up ~5 Kg but I am free from any cramping and edema. This is making paddle boarding time on the water much more enjoyable and safe. I'll gladly tote the extra 10-15 lbs of water. Maybe this has somthing to do with device and strips firing up, maybe not.

Teaser might be able to make more sense of this semi experiment with millions of variables

KATMEYSTER - we are pretty much on the same track - you go girl!! I like still using them to confirm if I decide to do a higher carb day that I've gone back into ketosis two days later.
THUD123 - looking forward to your data!!!

THUD123 - that IS neat data And you're doing really well too - congratulations!