Immediately after bariatric surgery, you will be put on, most likely, a liquid diet for a few weeks. After that, your surgeon will gradually advance you to soft foods and then regular textured foods. Once you're able to eat regular textured foods, here are some things that you should probably try to avoid, initially, or at least take your time in eating.
So, after weight loss surgery, you want to be careful eating anything that could expand when it gets wet. This includes really doughy breads or even sometimes rice. This isn't to say that you can never eat these things again, but the first time you try them after your weight loss surgery, you should try very small amounts because you don't want it to get stuck in your new small stomach.
Other foods that you should avoid after weight loss surgery are things that are very high in concentrated sweets. Things, obviously, like candy, cake, cookies, or other foods that are just high in carbohydrates, like pasta, bread. In small amounts they may be fine, but in particular, after the gastric bypass, your body might not be able to properly digest high carbohydrate foods and you may feel sick for a short time after eating them.
For the most part, after weight loss surgery you're able to eat most foods that you were able to enjoy before, however, just in much smaller quantities. And you also want to make sure that you take your time to chew very well and enjoy what you're eating.
So, these are just some examples of foods that you should avoid after weight loss surgery.