In a medium bowl stir together flour, oat bran, brown sugar, baking powder, baking soda, salt, nutmeg, and cinnamon. Set aside.
In a small bowl combine buttermilk, egg whites, and oil. Add to dry ingredients; stir just until moistened. Stir in shredded apple. Store batter, tightly covered, in the refrigerator for up to 3 days.
To bake, spray muffin cups with nonstick spray coating. Spoon about 1/4 cup batter into each muffin cup. Bake in a 375 degrees F. oven for 18 to 20 minutes or until a toothpick inserted near the center comes out clean. Makes 12 muffins (12 servings).