Canned beans have virtually zero fat, but it's important to drain and rinse them thoroughly to remove sodium from the liquid they're canned in:
Then, mash the beans into a paste. They'll have a pleasant flavor of their own, but they're also a blank canvas that you can adorn with whatever flavors or spices suit your taste:
I added a few drops of olive oilOne way to make this a little creamier, but you can leave that out or use something else as a thinner, such as lemon juice. You could use this as a sandwich filling, but I'm going to eat this batch as a salad, with some cucumbers and tomatoes:
Another possibility for making your sandwich spicy would be kimchi, or if you have the time, you can make your own spicy pickled cabbage in your refrigerator, as explained in this recipe for hasperat.