Ketosis is also known to help with many neurological conditions such as ADHD, depression, and to help with the elevated inter-cranial pressure suffered by our own dear Cori here on this board.
There is some speculation, unproven as yet, that a ketogenic diet could stave off or even prevent dementia.
All this is not to say that you have to be suffering from a major disorder in order to benefit from ketosis. It is not right for everybody but there is no reason not to give it a try if you would like.
I saw an interview on TV with that Dr. Phinney who just wrote the latest low-carb books. He is normal weight (looked rather thin) and says he's been in ketosis for 6 years--continually with no carb cycling. He's also a runner. He claims that ketosis is a positive state for the body, and he has never felt better or been healthier.
I don't measure ketosis, but I typically eat about 20g of carbs a day because I'm extremely carb sensitive, and this is the best way to manage my weight. I'm 71 and also have never been healthier in my life. It may be an individual thing--i.e., the fact that I am so carb sensitive may mean that my body works best on limited carbs.
The Ketogenic Diet for Health: Ketogenic Diets, Cortisol, and Stress: Part I — Gluconeogenesis.
I would think that if your activity level was vastly outside the parameters of your ability to produce glucose via gluconeogenesis (like HIT 2x/day or something) then that could be stressful, but lets face it....a program like that is not likely to be healthful anyway and your probably willing to sacrifice a bit of health for athletic ability. But I'm just speculating.
Read Vilhjalmur Stefansson's book The Fat of the Land. Very little discussion of ketosis or gluconeogenesis, but lots of discussion and examples of the healthfulness of a diet lacking anything except lean meat and fat. Not just healthy enough but actually superior health compared to mixed diets. It's really very fascinating.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Highest squat: 167.5 x 2. Current Deadlift: 190 x 3
different people will have different abilities when it comes to gluconeogenesis. some people's ability to produce glucose will be more or less robust than others. everyone will be able to produce enough glucose to refill liver glycogen - or you'd be dead. but the idea that your muscle glycogen stores will remain full on a ketogenic diet is fantasy.