you can lose weight, and even fat while eating bananas.....I know, I use to eat them all the time.
But once you start getting lower in body fat, its a different story. I have cut out fruit completely, except a piece here and there. Bananas are so high in sugar, if you want to eat fruit, eat oranges, or kiwis.
Just make sure you eat it as your post workout meal, best if its early in the day as well.
Fruit is not BAD at all, In fact, alot of people miss out from the health benefits fruit provides. But this is a bodybuilding board, and not a health board. Most BB's cut fruit out while cutting.