I haven't had weight loss surgery yet, but I did have gallbladder surgery 3 years ago right as my monthly cycle began to start. It's the same type of abdominal laparoscopic surgery and is not a problem. My nurse told me surgeons do it all the time unless they are working on your reproductive system.
They will not let you wear a tampon, you should not have anything foreign in or on your body but they will provide you a maxi pad. Make sure you let them know beforehand. It wasn't a problem for me with getting around or taking care of my personal needs and it did slow down the flow. Hope this helps.
