a cup of wheat bran has 125 calories and 2.5 grams of fat, while a cup of oat bran has 231 calories and 6.5 grams of fat. wheat bran is higher in fiber, with 25 grams per cup compared to oat bran's 14.5 grams. oat bran has more protein, but overall, wheat bran is more conducive to weight loss.