In a large bowl, whisk together flour, sugar, bran, flaxseed, baking soda, baking powder and salt.
In a separate bowl, whisk together bananas, yogurt, eggs, oil and vanilla. Pour wet ingredients over dry ingredients. Using a wooden spoon, stir together just until thoroughly moistened. Gently stir in chocolate chips.
Pour into a greased 9x5x3-in. (2-L) loaf pan or seven mini loaf pans. Bake in centre of preheated oven for about 50 minutes for large loaf, or 45 minutes for individual loaf cakes, or until cake tester inserted in centre comes out clean. Let cool completely on rack. (Loaves can be frozen for six weeks.)
Per serving: 209 calories, 5 g protein, 6 g fat (2 g saturated fat), 34 g carbohydrates, 3 g fibre, 32 mg cholesterol, 190 mg sodium