Preheat your oven to 375°F (190°C).
Cook the whole wheat lasagna noodles in boiling water according to package directions until al dente, then drain and set aside.
In a medium skillet over medium heat, add the olive oil and sauté the minced garlic for 1 minute until fragrant.
Add the lean ground beef to the skillet, seasoning with sea salt, black pepper, and dried oregano, and cook until browned.
Stir the marinara sauce into the cooked beef and let it simmer for 3-5 minutes on low heat.
In a small bowl, combine the part-skim ricotta cheese with the fresh spinach, mixing well to incorporate the greens.
In a small oven-safe baking dish, spread a thin layer of the meat sauce on the bottom.
Layer with half of a noodle sheet, followed by a portion of the ricotta-spinach mixture and more meat sauce.
Repeat the layers until all ingredients are used, finishing with a final layer of meat sauce.
Sprinkle the part-skim mozzarella and grated parmesan cheese evenly over the top.
Bake for 20-25 minutes until the cheese is melted and the edges are slightly crispy.