We made a few changes to lower the fat and calories, while still keeping the flavor.  Here's the skinny:  

1 1/2 cups vegetable oil > 1/2 cup canola oil plus 1 cup buttermilk
2 cups granulated sugar > 3/4 cup granulated sugar, 3/4 cup brown sugar 
3 cups all-purpose flour > 1 1/2 cups all-purpose flour; 1 1/2 cups whole wheat flour
Peeled apples > Apples with skin

For recipe performance:
Increased cinnamon to 1 tablespoon for flavor.

Nutritional Highlights

Prep Time:20 min

Start to Finish:2 hr 5 min

makes:20 servings

3/4 cup granulated sugar
3/4 cup packed brown sugar
1 cup buttermilk
1/2 cup canola oil
2 teaspoons vanilla
2 eggs
1 1/2 cups all-purpose flour
1 1/2 cups whole wheat flour
1 teaspoon baking soda
3 teaspoons ground cinnamon
1/2 teaspoon salt
3 cups finely chopped unpeeled apples (3 medium)
1 cup chopped walnuts

1  Heat oven to 350°F. Spray bottom only of 13x9-inch pan with cooking spray.

2  In large bowl, beat sugars, buttermilk, oil, vanilla and eggs with electric mixer on low speed 20 to 30 seconds or until blended. Add remaining ingredients except apples and walnuts; beat on low speed about 1 minute or until blended. Stir in apples and walnuts. Spread batter in pan.

3  Bake 40 to 45 minutes or until toothpick inserted in center comes out clean. Cool in pan on cooling rack 1 hour.

Nutritional Information

1 Serving: Calories 240 (Calories from Fat 90); Total Fat 10g (Saturated Fat 1g, Trans Fat 0g); Cholesterol 20mg; Sodium 150mg; Total Carbohydrate 34g (Dietary Fiber 2g, Sugars 18g) % Daily Value Vitamin A 0%; Vitamin C 0%; Calcium 4%; Iron 8% Exchanges 1 Starch, 1 Other Carbohydrate, 2 Fat Carbohydrate Choices 2