A frequent recommendation I’ve seen from those who (1) are fasting or (2) recommend fasting is to include meat stocks among the liquids you use to keep hydrated. They’re fairly low-calorie (probably under 100 calories for a cup) so they don’t break your fast, they’ll help keep electrolyte levels from getting out of whack, and the collagen (think “melted Jello”) in a decent stock fights off the hunger pangs.
The only trick is that you most likely want to use homemade stock…not the stuff you buy in cartons (which seems to mostly be flavored water) and definitely not the stuff you buy in cans (which is mostly very salty, flavored water). Beef stock can take 6-8 hours or more on the stovetop, but a pressure cooker (I have an 8-quart Instant Pot) knocks the total time down to about 2…fast enough for after work. I just knocked this together from recipes I’d seen, and it turned out pretty well for a first effort:
3 lbs. beef shanks and oxtails
1 large yellow onion, cut in eighths
2 carrots, roughly chopped or broken up
half a bundle of parsley
1 tsp black peppercorns
3 bay leaves
1/2 gal. water (more or less, to cover)
a few splashes of red wine
Roast the beefy bits at 450° for 40 minutes. Load the veggies and spices into the pressure cooker while you wait. When done, add the roasted beefy bits to the pressure cooker, deglaze the roasting pan with wine, and add the bits thus obtained to the pressure cooker.
Close up the pressure cooker and set it to run for 60 minutes at high pressure. Use natural release to bleed off the pressure at the end, open the lid, and use a strainer to fish out most of the meat, bones, and veggies. (Optional at this point: pull the meat off the bones, bag it, and freeze it for later use…in what, I haven’t yet figured out.) Pour the remaining contents through a colander into a large bowl to catch the remaining solids (maybe add some cheesecloth for more filtration). Have some right away after you skim off the fat, or refrigerate and remove the solidified fat tomorrow.