I have seen some individuals post on days they have zero net carbs eaten on a given day. What do you eat on days like that? I literally can't imagine getting that low!

Eat Meat. Drink Water.
If you want to know the basic premise of the zero carbers, here's a good website: https://zerocarbzen.com
You can also fast, zero everything.

Thanks! I've read about fat fasts, but I never saw the zero carb before. Thanks for the link!!

Not that I'm advising Zero Carb but there is a community of dedicated followers. Personally I think a healthy, real food LC plan with IF as needed is a better approach, but there are short term stall breakers of Very VLC like egg, egg and bacon or fat fasts, that work for some. I like vegetables too much to consider those beyond a few days.

One of my favourite studies involved giving otherwise fasting individuals 8 grams of glucose a day. Protein oxidation reduced by about the amount of protein that could have been used to produce that 8 grams of glucose through gluconeogenesis, blood ketones remained the same. So basically, these people were eating small amounts of carbohydrate, perhaps without actually increasing their carbohydrate metabolism.

So, if I eat an all-meat, zero carb diet, or add original Atkins induction levels of veggie intake, the amount that Dr. Atkins described as "effectively" zero carbohydrate--will there be much difference? I really don't know, it seems obvious that adding 8 grams of digestible carbohydrate to a zero carbohydrate diet will increase my glucose metabolism, but if you had to ask me before reading that fasting study, it might have seemed pretty obvious that that intervention should have increased glucose metabolism as well.

One thing I do know--certain micronutrients that I like to see in the green (at or near 100 percent of the largely made-up RDA's) are way easier to get there including low carb veggies in my diet, by the time I get a comparable micronutrient intake plugging in just various meats, I end up with a menu that's way less ketogenic, even though it's got less carbohydrate, protein just gets too high.