I find fried pork fat to be pretty close. Nuts or cream have too many carbs. Uncured bacon is another option, as it's only supposed to be for a few days duration to kick off ketosis in difficult cases. The fast I prefer now is PSMF. Again not a long-term plan for health reasons. The "fat fast" is meant for people who have a lot to lose?

https://skylertanner.com/2008/04/20...-crash-dieting/