There are plenty of misconceptions when it comes to weight loss, such as all carbs or fats are bad. The best formula for losing weight, according to the National Institutes of Health, is simple: Eat fewer calories than you burn. We've singled out five of the biggest myths that muddy the message.

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Myth #1: Carbs are bad, bad, bad.

The NIH recently completed a large study, with 811 participants assigned to one of four weight-loss diets with varying levels of fat, carbohydrates and protein — all with individual calorie reduction goals. The subjects were asked to stick to the specified percentages of nutrients and given menu plans. "After two years," says Catherine Loria, Ph.D., a nutritional epidemiologist at NIH, "we found no difference in weight loss at all." Still, some carbs are better for dieters than others. Dariush Mozaffarian, M.D., an associate professor of medicine and epidemiology at the Harvard School of Public Health, insists that not all carbs are created equal when it comes to weight loss. He led a study published this year in the New England Journal of Medicine that found that certain carbohydrates, such as refined breads and cereals, do seem more likely to cause weight gain than whole grains.

Myth #2: Don’t weigh yourself all the time: it’ll just worry you when it’s natural for weight to fluctuate.

Um, not really. Loria says that while she hasn’t studied this factor in a specific trial, she’s noticed that the biggest "losers" in weight-loss studies weighed themselves almost every day or every day. "It’s kind of hard for people to get on the scale," Loria concedes. You need to be aware of your weight, though, to make any necessary corrections in your diet. "There may be a couple of pounds day-to-day fluctuation that’s normal," she says, "but if you get beyond a couple pounds over your target weight, you probably want to rethink what you’re eating or increase your activity."

Myth #3: Just get out there and sweat — then you can eat whatever you want.

Exercise, obviously, is great for your health in myriad ways — from the psychological (it has been shown to help with depression) to building strong bones with weight-bearing activity. But there’s a caveat, warns Loria: "You have to be careful not to eat more calories than you just expended." Consult a fitness book or website to learn exactly how many calories your workout requires. That bike ride or long walk may not burn as many calories as you think.

Next: What about a no-fat diet? >>