alt Hacker NewsThere's 1655 calories in a pound of uncooked rice, so with 330lbs you are sitting at ~1500 calories a day for a whole year.
You wouldn't starve to death, but you'd absolutely want to supplement (both for more calories and probably for vitamins). But also you'd be eating that rice every single day pretty much, how else are you getting through that much rice?
Wouldn't you also need at least a little protein? and some lipids? For example, there is a lot more in Soylent than just rice flour. Oh, are we talking brown rice or white rice? That seems like it might make a huge difference, not only in nutrition, but also pooping.