Doughnut and pastries. Doughnuts will cost you 250 to 550 calories, but the 15 to 30 grams ofsugar in each is the real problem. With such a huge amount of sugar in a small package, your body pumps out loads of insulin to try to accommodate. A huge blood sugar spike leads to an even bigger sugar crash. This extreme up-and-down leaves you hungry soon after your breakfast — and you’ll crave even more refined carbs. It’s a vicious cycle of unhealthy eating that starts with the first doughnut. . . . The best breakfast foods give you fuel in the tank for energy that lasts. They boost your metabolism, fight disease and help keep your weight down.