@Antje77 - The source is basic chemistry - only proteins have nitrogen, so if you taste ammonia, that's because your body has some nitrogen to get rid off.
But in the interest of the forum rules (this really isn't a contentious point, so here's a link from runners world)
A low carbohydrate reserve is the usual culprit for burning protein, resulting in an ammonia odor.
In the context of a diet which is low in carbs and fat and sufficient exercise - what else is going to happen?
@Aurelie -
Firstly - please remember I'm not offering advice, you've done the obvious and sensible thing. DKA is for sure something that the medical establishment is worried about, because it can kill type 1 diabetics. DKA, however; is the
unregulated production of ketones, usually in the presence of high blood glucose.
Let me break it down.
Fats can be used for fuel throughout the body. for example the majority of the energy that is consumed in your heart is from fat. When glucose is present, the body will use that first, because as we know, lots of glucose in the blood is toxic.
So - if you always have "enough" circulating glucose, every part of your body can use that for fuel. That is the underlying reason why it's often described as the body's preferred source of energy. Muscle cells can just use glucose, where most other cells need insulin to tell them to use it.
Now, if you lower your blood glucose, by lowering carbs and exercising, insulin will drop, and 2 things will happen.
1 - your body will flip into using fat for energy. This is totally natural, and if you consider that we can store about a day worth of energy as glucose (a kind of animal starch called glycogen) but can store months of energy as fat, you can decide for yourself what that tells us about preferred sources of energy.
2 - fats are too big to pass into your brain, so that still needs a supply of energy. To cover this, your liver will continue to
create glucose, and also turn excess fat into ketones - these are like pre-digested fats - they are "clean energy" for the brain, but also may do some additional cleaning up work in the brain as well.
Now - what is happening in DKA, is that the brain is starving because the brain also needs insulin to use that glucose, and in a T1 in trouble, there is none, even though glucose may be through the roof - so the liver goes into panic production of ketones, which is enough to turn the blood acidic. However, in a person with a functioning pancreas who is not taking medication to drop insulin, the thing that regulates ketone production is ... insulin. So; ketone production is also totally normal. Babies are born in ketosis, and most animals are in ketosis most of the time.
The only thing that may be different in your case, is that you may not have excess fat, from your diet or otherwise, and so the liver will turn to protein to make ketones - the brain cannot be allowed to starve. Some of this protein will also be remade into glucose; and both processes result in some nitrogen having to be expelled from the body.
For me- one of the biggest changes I had to make was wrapping my head around the idea that fat is actually not the enemy. Sugar and starch is the enemy, and in that fight, you can actually use fat as an ally - it becomes your source of energy for more of the time.
What you do, of course, is up to you, but that's why you are being advised to take more carbs - the medical establishment struggle to advise taking more fat.. and essentially you have to do one or the other to avoid your liver having to use protein.
Ketosis may not be your goal. That's fine, but there is growing evidence that being in ketosis some of the time, is totally natural and beneficial for metabolic and mental health. In other words, there is nothing to fear about having measurable ketones (unless you are type 1 and also have high blood glucose - even Type 1 diabetics can benefit from ketosis, it's just a little more difficult).