I used to do that at a time when I did not exercise. The reason I chose dinner time was because it was the one meal I would eat with my family during the week, whereas breakfast and lunch (and the decision whether to have them at all) were more personal decisions.
It worked well for me at the time, and I dropped from 85kg to 73kg at a rate of roughly 1.0 kg per week. Once I got to 73, I plateaud.
Now I'm actually physically active, I eat 2-3 meals a day, but always dinner. For a monk, once a day should be fine (especially given how much food they tend to get offered).
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"The uprooting of identity is seen by the noble ones as pleasurable; but this contradicts what the whole world sees." (Snp 3.12)
"To argue with a person who has renounced the use of reason is like administering medicine to the dead" - Thomas Paine