Heat oven to 180 C° (350 F°) and fold a 20 cm (7.9 inches) loaf pan with parchment paper or grease with oil.
In a large mixing bowl mash the ripe bananas with a fork until completely smooth, then stir in egg, egg white, maple syrup, vanilla extract, ground cinnamon and a pinch of salt. Mix well, until you get a smooth batter.
Incorporate into the mixture the oat flour and the baking powder. Stir the banana bread batter, while gradually pouring in the milk. Start with little milk (about 1 tablespoon) and add up to 3 tablespoons (45 ml) only if the batter is still too dry.
Pour the batter into your prepared loaf pan. Bake in hot oven for 30 to 40 minutes, or until a toothpick inserted into the center of your low calorie banana bread comes out clean.
Remove the dessert from the oven and let cool in the loaf pan for about 15 minutes. Finally, take it out of the pan and let cool completely before slicing.