Preheat oven to 325°F (160°C).

Grease a 9 x 5-inch loaf pan.

In a mixing bowl, combine margarine and honey.

Add mashed bananas and egg to the mixing bowl and stir.

In a separate bowl, whisk together whole wheat flour and soda.

Add the dry ingredients to the wet ingredients.

Add buttermilk to the mixture.

Fold in chopped nuts.

Pour the batter into the greased loaf pan.

Bake for 1 hour, or until a toothpick inserted into the center comes out clean.

Let cool in the pan for 10 minutes before transferring to a wire rack to cool completely.