I have seen some pretty stupid descriptions of ketosis in regards to a low carbohydrate diet over the years but this one beats them all...
If the body doesn't receive sufficient carbohydrate, it breaks down muscle and other tissue to produce glucose.
This causes a build-up of waste products called 'ketones'. This is, known as 'ketosis' and is common in people who are starving, suffering from anorexia nervosa or who have insulin-dependent diabetes.
Ketones makes the blood acidic, in severe cases Ketosis can be fatal, particularly for pregnant women, unborn babies, and for people who have diabetes.
Finally, the heart may not be able to function to its full ability as ketone bodies are its main source of fuel.
So, not eating carbohydrates is bad for you.