Most people on this forum will probably respond subjectively: ie you’ll ‘feel this…’ and/or you ‘won’t feel this…’ The problem is that everyone is different and what one person subjectively experiences is not necessarily what another does. So many people end up frustrated and/or disappointed that they didn’t experience x or y the way other people talk about how great and wonderful it made them feel. Or they didn’t lose as much weight as fast as someone else so “there must be something wrong with me or what I’m doing”. How many posts have you seen titled “What am I doing wrong?” “Am I doing this right?” “Keto doesn’t work for everyone?”
There are, however, objective indicators. The first and simplest, and also the most denigrated, is the humble urine keto stick. You will continually read people say these things are useless and don’t waste money buying them. Spend your money on organic, grass-fed, free-range whatchamacallit instead. Here’s what keto urine sticks tell you:
After going onto the keto dietary regimen you will begin to detect ketones (primarily acetoacetate) in your urine. Detecting urine ketones is what is known as a ‘negative’ indicator. In other words, detecting ketones in you urine indicates you are in ketosis, but NOT yet and/or well fat adapted. So ANY ketones in your urine (does NOT matter how dark the colour, ANY) is a POSITIVE indicator of ketosis and a NEGATIVE indicator of fat adaptation/burn. In other words, you’ve reached first base. Congratulations!
As your metabolism and your cells and organs become better adapted to using ketones and fatty acids, your demand/utilization of ketones and fatty acids get more in synch. In other words, your liver no longer has to produce an oversupply of ketones to make sure everyone (cells and organs) has enough fuel to burn. So there is less and less excess to be excreted in your urine.
At some point (days, weeks?), you will have NO urine ketones. In other words, you’ve reach second base. Congratulations! If you remain in ketosis by keeping your carbs sub-20 grams per day and eat a keto-rational ratio of fat:protein, the urine keto sticks should show NO ketones in your urine. So you can use one from time to time to confirm. Totally objective, no subjective this or that.
[EDIT] See this topic for some very interesting reports about urine ketones after fat adaptation.
Once you get to the point where the lowly urine keto stick shows no ketones consistently over a few weeks, you can then consider other tools available to test/confirm the byproducts of ketosis and fat metabolism: ie blood meters, breathalyzers. These tools are not necessary, but provide interesting and somewhat useful information; and, if you have some medical condition perhaps necessary information.
Bottom line: if you are eating sub-20 grams of carbs per day and are still conscious and functioning, then you are burning fat. The longer you burn fat efficiently, the more efficiently fat adapted you get. Long term, I suspect the most useful objective indicator of fat adaptation is breath acetone (BrAce) and glucose. However, the jury is still out.
