Sound familiar? Welcome to the infamous Diet Plateau. After making a mountainous effort to exercise and eat right, you find your weight loss results have hit level ground. But you're not alone up there. Diet plateaus are very real, usually occurring four weeks to two months into a diet, says Roxanne Moore, R.D., the coordinator of Nutrition Education at Townson University in Baltimore, and a spokesperson for the American Dietetic Association.

A diet plateau can result from several factors. It may be a question of what, exactly, you're losing. "Seventy percent of the weight you lose in the first two to three weeks of a diet is water," explains Moore. "By the end of the third week, water loss will account for only about twenty percent of weight loss. Once you begin burning body fat rather than merely shedding water, you have to work harder." How much harder? Most people can lose a pound of water weight a week by cutting their daily intake by 200 to 300 calories, she says. Losing a pound of fat a week requires cutting about 500 calories a day.

Consuming too few calories also can waylay weight loss. "You need a certain amount of calories for everyday functioning. If you try to lose weight too quickly by radically reducing calories, your body will slow your metabolism to compensate, creating a weight-loss plateau," says Moore.

Other diet derailers include underestimating portions—essentially overeating without realizing it—and consuming hidden sources of calories, such as excess fat used in meal preparation. You also may not be working out at the right exercise intensity, thereby overestimating the calories you're burning at the gym.

The good news is, according to Moore, you can kick your diet up a notch to drop those last pounds. Here's how.

Consume the Correct Number of Calories. Eat enough to maintain weight loss at a pace of one to two pounds per week. "If you're losing more than two pounds of body fat a week, some of that weight loss is coming from muscle. When you lose muscle mass, you slow down your metabolism," says Moore.

Exercise. Do some form of aerobic exercise three to five days a week and strength training two to three times a week. Strength training maintains and/or increases muscle mass, helping boost your metabolism.

Start a Food Journal. Recording what you eat make you aware of extra calories. That handful of Doritos you shove in your mouth will affect your body, even if it came from a bag on someone else's desk.

Be Patient. "Sometimes we need to allow the body a period of time to adjust, and then weight loss will resume," says Moore. "If it doesn't resume within four weeks, have your diet and exercise program analyzed by a registered dietitian."

The bottom line: Take time to congratulate yourself on having come this far. Then adjust your routine to carry you to weight-loss victory.