Breakfast comes at a terrible time of day to make a rational decision. We're rushed. We're groggy. And we're famished. We know it's good for us — 90 percent of Americans think it's the most important meal — yet fewer than half of people actually eat it regularly, according to the International Food Information Council.

Unlike other meals, however, breakfast is unique in that it can set the tone for your entire day — for better or for worse. The trick is knowing how to eat it.

There is no perfect morning meal because the best breakfast depends on your body and individual nutritional needs, but you can't go wrong by eating "a moderate meal of mixed foods," said Richard Mattes, a professor of food and nutrition at Purdue University in West Lafayette, Ind. Start experimenting, using our guide below to see how common breakfast combos will affect your day.

BAD, BAD, BAD: No breakfast at all

Some people say they're not hungry when they wake up, but because you've fasted all night, your metabolism — and fat-burning ability — slows down. Those who skip breakfast are also more likely to be overweight and eat more fat and calories the rest of the day, said Susan Biali, a Vancouver physician who specializes in dietetics. Bypassing breakfast also makes you less productive and less likely to excel at school or work. If you think eating breakfast makes you hungrier the rest of the day, you're probably starting off with too much sugar. But if you're wrestling between a bad breakfast and no breakfast at all, choose the doughnut and try to limit how much you eat.

BAD, BAD: Coffee or tea only

A daily cup of coffee or tea gives you some hydration and a jolt of caffeine. Research has also linked both drinks to a variety of health benefits. But while it might hold you over until lunch, "it's only the hot liquid that is filling your stomach, tricking you into feeling satisfied," said Janel Ovrut, a Boston-based registered dietitian. "You likely wind up overeating come lunch, when you're famished."

To jump start your metabolism, add a piece of fruit, suggested Ovrut.

BAD: Coffee or tea, plus a doughnut

It's quick, easy and yummy, but you'll pay a steep price for the 90-minute sugar high. Doughnuts are a famously high-calorie, high-fat, high-carbohydrate breakfast that will leave you feeling "stuffed, sluggish and even sleepy," said New York registered dietitian Constance Brown-Riggs. Sadly, bagels, muffins and sugary cereals also "spike your blood sugar and set you off on an energy roller coaster for the rest of the day," said Tara Coleman, a clinical nutritionist in San Diego.

A breakfast bar and orange juice might seem healthier, but "it's not much better than eating a candy bar and sugar cubes, said John La Puma, a physician, chef and author of "ChefMD's Big Book of Culinary Medicine" (Crown, $24.95).

Think of juices as desserts because "their sugar content hypes up your insulin level and craving for real, gut-filling food, said La Puma. Avoid sugary foods in the morning altogether. If you're going to eat a breakfast bar, try to sit down and eat it slowly, La Puma said.

BETTER: A bowl of low-sugar, high-fiber cereal with no-or low-fat milk, banana, whole wheat toast and jam and coffee

Choose cereals that have at least 3 grams of fiber and less than 10 grams of sugar, such as Cheerios, Kashi's GoLean, All Bran or Fiber One. Skip most cereals with mascots because research shows children's cereals have more calories, sugar and sodium than those without a licensed character. Still, although this breakfast provides a little fiber, some protein and some vitamins from the fruit and cereal, it's high in processed sugar, wheat and caffeine, said registered dietitian and weight-loss coach Ilona Fordham.

"It won't provide long-term energy, and by midmorning a person will want more caffeine," Fordham said.

By lunch, you'll be hungry and may feel like overeating all day long.

BEST: A hard-boiled egg and a bowl of slow-cooking oatmeal topped with berries, walnuts, raisins, flax seeds or sunflower seeds — with coffee or tea

This meal is a nutritional powerhouse and easy to pull off if you make the oatmeal and the eggs the night before. Fiber and protein help slow down the digestive process, making you feel full longer and keeping your blood sugar steady.

"The protein from the milk and nuts, combined with the healthy carbohydrates, will eliminate any sugar crashes for at least three hours," said Melissa Hawthorne, a Houston-based registered dietitian.

"Flaxseed and walnuts are an excellent source of omega-3 fatty acids, which have been shown to lower LDL (bad) cholesterol, reduce inflammation and reduce the risk of heart disease," Hawthorne said.

To make this meal even better, add good fats by spreading peanut butter or avocado on whole grain toast or an English muffin.

Is it OK to eat a big Sunday brunch?

Cold cereal is the most popular breakfast food during the week, but on leisurely weekends, we love to let loose. We devour traditional breakfast foods such as eggs, bacon, sausage and pancakes, according to the market research company Mintel.

Fortunately, the weekend binge isn't likely to have a huge negative effect because "eating healthy is all about balance," said Timothy Harlan, a professor of medicine at the Tulane University School of Medicine, who produces the nutritional Web site www.drgourmet.com. "Sure, you can eat perfectly 21 meals a week and be healthier, but at what price?"

Sunday brunch is a special part of countless family rituals, said Harlan. That alone can have health benefits.

"Having a large, friendly meal works for all of us on a social level that transcends the perfect diet," he said. "It's the same with eating out," he said, meaning it's fine to indulge in the special splurge meal every now and then.

Also, the very term "brunch" means you'll eat only two meals on Sunday. So even if your meal consists of fatty and caloric foods that can have an immediate effect on blood pressure, you have a chance to take in fewer overall calories.