I might be able to offer a bit more information in addition to what the other person wrote (I have visited but never joined):

They were still doing this the last time I visited in the mid-2010s; eating two meals a day rather than three. The explanation I received was that they originally did it several years earlier as a sign of solidarity for those who didn't have enough to eat (or something similar to that effect). Kind of like a fast to help them remain mindful of the misfortunate. Then, they decided to make the change permanent, citing health benefits (maybe some other reasons too, I forget).

It is a strange practice, but it didn't seem like there were any ulterior motives behind it. There was always plenty to eat at the other two meals and opportunities for snacks throughout the day. It also seemed like everyone had gotten used to it by then, but I would imagine it was a tough transition. I remember how weak and tired I felt during my first (missed) supper the first time I visited.