Please don't think Atkins or Asprey. Those are pretty much unsustainable— either for you or the environment. This is not that.
The ketosis we're talking about is practically a vegetarian ketosis. Certainly very, very plant forward ...
... strategically supplemented, as required by each individual constitution/genetics, with mostly unsaturated oils found in the SMASH fish, avocados, flax, chia, hemp, nuts & seeds. And the oils: olive, coconut, even palm.
Think Barcelona without the bread. (And the sweets. And, sorry, most of the Priorat, cava + vermut.)
Doing this as a strict vegetarian or even vegan is not impossible, but getting the necessary fat could be difficult for some, and of course there are essential nutrients missing in an all-plant diet, so particular vigilance/monitoring needs to be exercised.
If you're doing dairy, goat and sheep's milk -based products are preferred. Pasture-raised, of course.
Folks already in relatively decent metabolic shape can benefit from spending 3-4 weeks in ketosis 3-4 times a year. But many make it a lifestyle. For the rest, especially folks with cognitive, cardiometabolic or energy concerns, Dr. Sandison recommends aiming for 6 months (or more) of the year.
"Sat fats" are not necessarily a no-no, even for ApoE4 carriers. Simply monitor markers to see what works and doesn't work for your body. Biochemical individuality and all. Dr. Sandison shared that many of her "3/4's" and even "4/4's" actually saw their blood lipid panel numbers improve while doing the pure (no fat restrictions) program— while some of her "3/3's" ended up having to cool it on some of the saturated fats (e.g., eggs, full fat dairy, meat), so you really don't know until you dig it (and monitor)!
How To Measure? The most reliable way to measure, Dr. Sandiston has found, is via blood with finger prick and test strip. (Measuring urinary ketones can be okay for the first month or so, but after that it's not really a reliable method. She has also found the pricey breath ketone meters inconsistent.) She likes the Keto-Mojo, and there are 3-4 similar brands for a bit less. (I see K-M on you-know-who for about $49.
What Level of Blood Ketones To Aim For? To start, the goal is to get a reading > 1.0. Between 0.5 and 0.9 is mild ketosis, so give yourself a pat on the back even if you are in that range to start— but the ultimate goal is to get up over 2.0.
How Long/Often Should I Try To Be In Ketosis? People doing this kind of preventively can do this 3-4 times a year for 3-4 weeks at a time (for example, one month each quarter), but they might discover that they feel so good in ketosis that they might want to do it forever! People already experiencing some brain fog or more substantial cognitive/neurological issues will want to do this for a minimum of 6 months each year, and it's easier for most to do it in actual six-month chunks because it can take a while to actually get into ketosis but is easier to stay there once you've arrived! Exercise seems to nudge most bodies (but not all) in the direction of ketosis, so this is not exclusively driven by food choices (<60 grams of carbs daily + more healthful fats) and fasting.
Is There Anyone Who Shouldn't Try This? There are, of course, gentle warnings about people with kidney disease, but that applies more to the Atkins/Asprey idea of ketosis that has you eating T-bone steaks and butter all day. This is not that. (Heck, even Mayo Clinic is copying us.) If you are underweight or struggling to put on/keep on weight, you might want to spend a little time figuring out why this is so (look into stress, hormones, toxicant exposure, stomach acid/bile acid sufficiency, protein and even caloric sufficiency, etc.) before embarking on this program because many people, at least initially, do lose weight. And it's easier to get into and stay in ketosis if you have a little extra body fat somewhere from which to draw when needed. So-called "exogenous" ketone supplements can help some, especially thin, folks in the beginning. These include things like MCT oil but also ketone esters and salts. I will paste in 3 examples below.
(some may wish to read, "How To Avoid the Keto Flu," external link)
Do I Have To Do Extreme Intermittent Fasting To Make This Work? The biggest surprise for me while listening to Dr. S field these questions yesterday was finding out that her Marama residents are eating THREE MEALS A DAY with TWICE DAILY SNACKS! And still they are managing to get into and stay in ketosis. The cool/don't-have-to-think thing about the Marama (and now Clear Mind Center) residential experience is that since the only foods available are all "ReCode Approved" food choices, the residents can pretty much eat anything and everything they want. That's one big, big benefit of the residential experience. Perhaps the biggest.
While it's a tiny bit more extreme than what Dr. Sandison appears to be doing at Marama, the original KetoFlex 12/3 plant-forward ketogenic eating plan was developed, of course, by Dr. Dale Bredesen and his Apollo Health team, so they are still the default experts. Those details can be found at the Apollo Health website here.
Hoping that someone somewhere finds this helpful.
P.S. I see that Jacob Gordon (mybiohack.com) does a nice job of presenting the KetoFlex 12/3 plan from his personal experience, with only 2-3 statements I would quibble over. You might check it out or simply search "recode diet plan" or "ketoflex 12/3."