Donuts are typically high in sugar and carbohydrates and low in protein. Research from the March 2009 issue of the "British Journal of Nutrition" suggests that increased protein intake at breakfast can help you feel fuller throughout the day, which aids in weight management.
According to the nutrition information provided by online food database My Fitness Pal, one maple bar donut contains 460 calories. One maple bar contributes 23 percent of your daily calories in a typical 2,000-calorie diet.
Maple bar donuts are high in fat; one donut contains 29 g of total fat. Of this fat, 4 g comes from saturated fat. MayoClinic.com notes that saturated fat intake should be limited, as it may increase your risk of heart disease.
Maple bar donuts are also rich in carbohydrates. My Fitness Pal notes that each maple bar donut contains 44 g of carbohydrates. Of these carbohydrates, 11 g come from sugar, while 2 g come from dietary fiber.
Maple bar donuts are quite low in protein; each donut contains 6 g of protein. The Harvard Medical School notes that this is the same amount of protein found in just one egg, which is much lower in calories.