Spinach? I buy it in those frozen nuggets. Each nugget is about an inch wide. Even if you take a foot, that's only about 4 grams of net carbohydrate.

How are you checking ketosis? Urine strips? They can tell you that you're in ketosis, they can't always tell you that you're out. I do some intermittent fasting, in my last two 24 hour fasts, my urine ketones actually went down, back up to deep purple, gradually, over days of refeeding. The probability that my blood ketones went down during the fasting is low. Urine ketones are regulated by the kidneys. If you are wasting sodium, ammonia, etc. in your urine, that's alkaline, something acid needs to balance it, ketones fit the bill.

Restricting to 50 grams of carbohydrate might be sufficient for some degree of ketosis in many people. But for me--very likely I'll be too shy or depressed much of the time to even make comments like this online, and I'll be much more prone to binges. Not everybody needs to be in a deeper ketosis, it's not necessary to weight loss, but it is worth pursuing for some people.