I do this every year as a part of Ramadhan. Though I am not very religious - fasting and taking a break from the usual each year is uplifting, deeply spiritual and of course has health benefits..
Basically on the 11th day after full moon and new moon, one fasts from sunrise to sunset. That’s twice a month. It’s called Ekadasi Fast.
But the real trick is preparing to fast 6-8 hours before and after the day of the fast.
Also the day after the fast, the food has to be grain/gluten free(rice seems to be ok) and has certain ingredients like greens, herbs and spices. It’s very light.
Full moon and new moon days are always food for milk and fruit fasts. And there is a whole bunch of other religious day fasts. Example: no salt on 6th day after full/new moon..a lot of ingredient restrictive fasts etc. I don’t know a lot about that but I have seen my mother observe it. I must find out more.
There seems to be a whole method to the madness and when scheduled properly, one can do staggered and scheduled partial fasts 6-7 days for a lunar fortnight. The calorie restriction mostly comes from the rules against certain ingredients.
Even in the pared down format I follow, I feel like I connect more with my food and am more mindful when I cook. Most of all, I don’t waste as much food because it’s so much work preparing the food! Of course, it’s seasonal. Having said that, I guess annual menu and schedule format has to be reversed for those in the Southern Hemisphere.
Your best bet is to connect with someone in your community or local temple and ask them.