This is one of those "ymmv" type of things. There are a few possibilities, listed in order of liklihood. One: there were carbs in the stuff that you mighy have missed. Two, you ate way more than you think you did. Three, your body has a higher rate of gluconeogenesis than is normal.

I am personally maintaining nutritional ketosis on a diet consisting of 90-95% protein, but it's also extremely low in calories, and I am still running a lifting schedule.

collegefbfan wrote: »

What is ymmv

Your mileage may vary.

My recent understanding is that even too much protein can knock you out of ketosis. Fat is the only macro that won't do that.

cdebracy wrote: »

collegefbfan wrote: »

What is ymmv

Your mileage may vary.

My recent understanding is that even too much protein can knock you out of ketosis. Fat is the only macro that won't do that.

It can, but it's not likely unless there's carb involvement as well. Gluconeogenesis is a fairly slow and controlled process. It doesn't slam you all at once with blood sugar like carb intake does. However, the line is pretty thin in my experience. I don't want more than 2-4g of carbs (unless fiber, then 5-8g) in a sitting accompanying high protein intake. That's about the line for me.

The process of your liver converting aminos into glucose.

collegefbfan wrote: »

So like I said we were at the boat show this weekend. Tons of protein rich foods, not much on the fat side of things. Especially not the keto kinds of fat. We get home and tested with blood strips. We were about 1.4 Thursday night before we left. Tonight I was 0.1 and the wife was 0.4. She even drank alcohol. I know one does not constantly stay in ketosis. But please tell me this for future reference..
Was it the lack of fat?
Or what else?
How long does it take to get back in?

It wasn't the lack of fat. You don't get into ketosis by eating fat. It has only to do with the amount of glucose in the blood. Which it seems in your case, would've been from something you ate.
You tested at 0.1, so you are still in ketosis. It's just very low levels. Even if you tested at zero, it could be as little as an hour or two to get back to making ketones. It doesn't take long. Just have to wait til the glucose and therefore, insulin, comes back down.

cdebracy wrote: »

collegefbfan wrote: »

What is ymmv

Your mileage may vary.

My recent understanding is that even too much protein can knock you out of ketosis. Fat is the only macro that won't do that.

This is really only true for insulin resistant people. However, so many people are that it is a common issue.

I could get measurable ketones again within a day or two of very LCHF. Faster if I cut my calories more than normal or fasted. Or exercised intensely - that helps.

The longer I was in ketosis, and losing weight, the faster I seemed to get back into ketosis.