Preheat oven to 180°C.

Lightly spray a 21x11cm loaf pan with oil and line the base and two long sides with a piece of non-stick baking paper.

Combine the margarine and sugar in a large mixing bowl and beat with electric beaters until light and creamy.

Add the eggs one at a time, beating well after each addition, until the mixture is pale and fluffy.

Mash the bananas and stir into the mixture with the buttermilk using a large metal spoon to combine well.

Sift the flour, bicarbonate of soda and cinnamon together into a mixing bowl, add the oat bran and stir to combine.

Add to the banana mixture and fold in until just combined.

Spoon into the prepared loaf pan and smooth the surface with the back of the spoon.

Bake the banana bread for 50-55 minutes or until a skewer inserted into the centre comes out clean.

Stand in the pan for 5 minutes before turning onto a wire rack to cool.

Store in an airtight container in a cool place (but not in the refrigerator) for up to 4 days.

Recipes reproduced with permission from The Low GI Family Cookbook by Kaye Foster-Powell, Anneka Manning, Professor Jennie Brand-Miller and Philippa Sandall, Hachette Australia 2008.