If you're trying to lose weight, it's the amount of calories that you consume in a day that play a big factor... 1 liter of orange juice is roughly 450 calories... that's a lot of calories that are adding no real satisfaction to your diet - No fiber to aid in fullness (or help with elimination) no protein... There's really nothing being added...
So if you're factoring i those calories... then you won't gain weight but you're calories are probably better spent on something that will help you long term.