There are two things you can do to keep your ketones consistently high:  
1) Fasting  
2) Limit carbohydrates 
 

The physiological basis for these two to increase ketone body concentrations is

It's all about not inducing blood sugar spikes.

 

Why would suppressing blood sugar spikes lead to a constant increase in ketone body levels?
 

For this you need to understand the hormone "insulin".
Insulin secretion is induced by a blood sugar spike, causing a phenomenon called an insulin spike.
When an insulin spike occurs, all the enzymes that synthesize ketone bodies are suppressed, and all the ketone body synthesis systems are shut out.

 

normal diet (about60% carbohydrates), ketone bodies are unlikely to increase.
sugar if possible30-40%If you eat a diet that is suppressed to0.2~0.3I think it goes up to about millimoles.
Also, it is said that you can expect various effects of ketone bodies to some extent.