Preheat oven to 350 degrees. Coat a 9 x 5 inch loaf pan with nonstick spray and set aside.
In a large bowl, use a handheld mixer to combine ripe bananas, nonfat yogurt, eggs, butter, and sugars. Blend until bananas are mashed and mixture is combined.
In the same bowl, add in the flour, ground flaxseed, chia seeds, cinnamon, baking soda, and salt. Mix until batter is combined.
Pour the batter into the greased loaf pan. Bake on center rack in oven for about 55 minutes to an hour, or until a toothpick inserted in the bread comes out clean. Let cool in pan for 10 minutes before removing bread from pan and letting cool on wire rack completely.
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Notes
This is a great make-ahead banana bread recipe. Store in the refrigerator in an airtight container for up to a week.