At least at the Dharma Drum Mountain retreats I've been to, it's true they have restrictions on what to eat and when. For example, garlic is contra indicated, offensive smell and supposedly makes you randy. Eating dinner is contraindicated, offered, but you'll notice the monks not eating it and just having tea or something. It's considered a medicine meal for the sick. Personally, I do feel more restful and ready for sleep at the end of the retreat days without dinner, but I do see how people not used to it could consider it food deprivation.