[bstrand]

Sounds like you played with starvation and lost.

Ketosis does not require or imply a severe caloric deficit. It requires a very low carbohydrate intake, but you can eat a maintenance level of calories and be in ketosis.

None of the standard guidance (e.g. [1]) for a weight loss program using a ketogenic diet advocates such a severe deficit. Presuming you're a male of average height, 700 kcal is about a 75% deficit. By all appearances, that was the source of your troubles, not keto per se.

I'm glad you recovered all right!

[1] http://keto-calculator.ankerl.com/