Can anyone explain how 2 weeks post op when you start eating under 1,000 calories a day you gain weight and walking 45 mins a day. It just dosent make sence, when pre op I could take in 3500 cals a day and not gain weight. I just dont understand and am very frustrated. Please help!

You're still recovering. Surgery is very traumatic to our system. Some systems react by retaining Water. I'm sure it's just water retention. If you can up your water intake, it will help.

Hang in there...the best is yet to come

Yep, a lot of that is water retention. Also, your body is adjusting to the new eating style. It will go in and out of "conservation phase" (hoarding all calories you put into your body), which will cause plateaus. If you are TRULY taking in fewer calories than you are expending, it will eventually reverse itself and the weight will start to drop off. And zounds! You could eat 3500 calories and not gain???????? Are you a 6'4" man or something?