hi Bob,
Yes, the ketone sticks detect and measure the presence of ketones in the urine.
By following a very lowcarb diet such as Atkins, once you've cleared out all the carbs from your system, your body will begin to break down it's fat stores into fatty acids. These fatty acids go to the liver, where they are made into ketones, which can be used by the muscles, the brain and other tissues and organs as a very efficient FUEL ..
.. When there is an excess of ketones in the bloodstream, they will "spill over" into the urine ... and their presence can be measured with the ketone test strips.
However, the liver will also make ketones from the fatty acids of DIETARY fat as well ... so if you've eaten a rich, fatty lowcarb meal .... Also, the liver will make ketones from alcohol; in fact it will use alcohol in preference to fatty acids ... so your fat-burning will go on hold when you drink ... but you will still be producing ketones.
So, the test strips have no way to tell the source of the ketones, only that they are present. There are some folks too, who seem to always test negative or trace only ... yet they are burning fat and are in ketosis. It may be that their body is using all the ketones as fuel, so there's no "excess" to spill into the urine.
Bottom line, the ketone strips are a useful guide to see if you're on the right track, but they are not the be-all and end-all of lowcarbing. I've seen so many people get really hung up --- quit in frustration even -- because they can't get the sticks to "turn". Other folks follow Atkins just fine and never use the sticks even once. Best indicators for lowcarb success -- take your measurements with a tape and follow weight loss averages (because there WILL be up and down fluctuations) on the scales.
Doreen