Why is calorie counting so popular? As Americans, we love easy sound bites, Bowden says. Counting calories (or fat grams) is far easier than actually understanding the complex effects food has on our bodies (and our waistlines). Calories do count, but they are far from the whole picture.

"Food produces hormonal effects in the body," he says. "Some hormones say 'store that fat'; others say 'release sugar'; others say 'build muscle.' Study after study shows that diets based on the same amount of calories, but different proportions of fat, protein and carbohydrates, result in different amounts of weight loss."

Why It's Hard to Keep Count

It is also extremely difficult to count calories accurately. Although 67% of Americans report taking calories into account when making food purchases, nearly nine out of 10 have no idea how many they actually need, a survey conducted by the International Food Information Council Foundation reports. We tend to miscount what we eat, as well. Although the U.S. food supply produces 3,900 calories for each person per day, men claim to eat an average of 2,618 daily calories, while women report eating only 1,877.

Where do those missing calories go? Into our mouths and directly to our waistlines, for the most part. In fact, there's a lot working against us when it comes to staying slim and healthy. Big meals and large portions (think holiday feasts and most restaurant dinners) tend to undermine our calorie-counting efforts, studies show. And being overweight makes it even more likely that we'll underestimate the calories in our meal --a definite disadvantage when it comes to losing weight. In one study, published in the Annals of Internal Medicine, researchers found that all people, no matter what their size, are more likely to be able to accurately guess the number of calories in small meals than in large ones. Overweight people tend to eat larger meals and larger portions, which explains why they tend to make mistakes counting calories, researchers say.

Even nutrition experts aren't exempt. When Young showed 200 dietitians five different meals actually served in restaurants (lasagna, Caesar salad with chicken, tuna salad sandwich, steak plate and a hamburger with onion rings), their estimates of the number of calories in each meal were woefully inadequate. Some meals contained double the calories that some nutrition professionals predicted they did.

So why do we keep counting calories? For the most part, because it's what we're used to doing -- that is, following a mathematical formula of body weight equals calories in -- calories out, says Steven Aldana, PhD, professor of lifestyle medicine at Brigham Young University, and author of The Culprit and The Cure and The Stop and Go Fast Food Nutrition Guide.

Calorie Counting Alternatives

"The formula is still correct," Aldana tells WebMD, but since it's hard to count calories outside the lab, you may want to pursue other methods of policing your energy intake. Think of your workouts, Aldana says. When we exercise, we're burning calories, but we rarely ever count calories when we're calculating how much exercise we need. Instead, we count miles, minutes, or heartbeats.

Ready to jump off the calorie-counting bandwagon? Here's what to do instead:

• Instead of counting calories, eat smaller portions. It may seem like a basic concept, but it's easy to forget that bigger portions have more calories. Most of us gauge a serving as "the amount we're used to eating," a recent study found. That would be restaurant food -- where meals are served on platters, not plates. And the more we look at (and eat) huge portions of food, the more we see them as normal -- to the point of serving ourselves the same amounts at home. Unfortunately, studies show that when we're served more, we tend to eat it. When researchers from the University of Illinois, Urbana-Champaign served subjects bigger helpings, people ate up to 45% more food. One caveat: there's no reason to eat fewer vegetables; they're much less calorie dense than other foods (they contain fewer calories per gram). A cup of raw broccoli, for example, contains only 31 calories, while the same amount of chocolate ice cream boasts close to 285.
• Instead of counting calories, choose foods that use more calories. Some foods require more energy than others to digest and metabolize, says John Berardi, PhD, CSCS, president of Precision Nutrition, and author of The Metabolism Advantage. We call this the thermic effect of food, Aldana says. The difference is very small, he cautions, just a few calorie's difference, for example, to eat a slice of bread made from whole grains vs. one made from refined flour. (Refined flour digests easily, leaving you with the full 4 calories per gram, while whole grains use up part of their 4 calories per gram during the digestion process, he says.). For example, if a woman were to start eating only foods that take a lot of work to digest (high-fiber, protein foods) she might save about 12 to 15 calories per day, the same amount she could expend by walking for about four minutes. But for some people -- especially those stuck in sedentary jobs or crunched for time -- it just may be worth it. Besides, foods that take more work to digest, like those high in fiber, tend to be those that are better for you. And choosing the best nourishment for your body is a much healthier food focus than counting calories.
• Instead of counting calories, make sure you consume the right kind. Nearly one-quarter of Americans' calorie intake comes from sweets, desserts, soft drinks, and alcoholic beverages, research from the University of California, Berkeley notes. Another 5% comes from salty snacks and fruit-flavored drinks. Nutrient-rich fruits and vegetables, on the other hand, contribute only 10% to the average American's calorie budget. "When it comes strictly to weight loss, a calorie is a calorie, Klein says. However, when it comes to your health, it's best not to blow your calorie budget on foods that lack nutrients. Nutrient-dense choices like fruit, vegetables, and whole grains can help prevent heart disease, cancer, and diabetes, while those lacking in nutrients, like candy, soft drinks and white bread can contribute to a whole host of health problems.

The bottom line? You don't need to count calories, but you should make all your calories count.