How long until I lose the weight caused by Zyprexa and will my Invega interfere with my weight loss?

Hi, Chantellah!
Zyprexa is very notorious for weight gain and most people taking it will at least gain some weight. Some people will gain as much as thirty pounds or more. Once you're off it, depending on factors like your dosage and your personal metabolism, you could expect losing within just a couple of weeks.
Invega also can cause weight changes although not nearly as frequently and they can go either way... loss or gain. Just because you gained weight on Zyprexa doesn't necessarily mean that you can't lose the weight while taking the Invega.
Best regards and here are some statistics to compare the two medications:
INVEGA
"Common (1% to 10% of users): Decreased appetite, decreased weight, increased appetite, increased weight"
ZYPREXA
"Very common (10% or more of users): Weight gain/increased weight greater than/equal to 7% of baseline body weight (up to 89.4%)"