1. Preheat the oven to 350° Fahrenheit or 176° Celsius, and grease a 9x5 inch loaf pan. Set the pan aside.
2. Stir the flour, protein powder, sweetener, cinnamon, pumpkin spice, baking powder, salt, baking soda, and optional chocolate chips to a large mixing bowl.
3. Whisk in the pumpkin puree, eggs or water, oil or yogurt, and pure vanilla extract until just evenly mixed.
4. Spread into the prepared pan. Sprinkle extra chocolate chips or a handful of diced pecans on top if desired.
5. Bake on the oven's center rack for 45 minutes or until a toothpick inserted into the middle of the protein pumpkin bread comes out mostly clean. (After about 30 minutes, if you notice the top is browning too quickly, you can create a loose tent out of tin foil and continue baking.)
6. Let cool on the counter before slicing and serving.
7. Once cooled, store leftovers loosely covered on the counter overnight or covered and refrigerated for up to five days. Or slice and freeze for up to two months.