Fiber is not a magical bean that will grown the weight loss bean stock.  Weight loss is all calories.  That being said, fiber makes you feel more full and may help you reduce your intake.  I recommend at least 35-45 grams of fiber per day while you are trying to diet.  Do I think it will work all dieters, absolutely not, but it does work for me.  

Warning:  Whole grain is not always whole grain.  Watch the labels.  If it does not have 5 grams of fiber or more, choose something else.