This can be a discouraging time for a dieter, and what's worse, it can last from a few days to a few months. Here are some tips for hanging in through this frustrating period:

First and most important, you should evaluate how you feel. "Don't just focus on the numbers," Zelman says. "Do you have a little extra zip? Are you sleeping better? Feeling healthier? More energetic?" You are probably continuing to benefit from your workout and diet even if you are not seeing results in your weight.

Now it's time to take action. "When your body becomes resistant, you need to make an adjustment," Zelman says. She does not suggest cutting food to someone who is already on a low-calorie diet. "You can't be hungry all the time," Zelman explains. "That discomfort would contribute to a lack of success in losing weight." Instead, she advises adjusting your exercise routine. "Increase the duration or intensity of your workout," she says. "You may need to walk a little further or a little faster." If you haven't already, introduce weight training to your regimen. Lifting weights builds muscle mass, and muscles are more active than fat (or they chew up more calories).

Don't become scale-obsessed. You have normal weight fluctuations, which will be reflected on the scale every day. Seeing these natural fluctuations can be frustrating and sabotage your goal. Zelman recommends weighing yourself once a week under consistent conditions, perhaps when you wake up, in your underwear, after emptying your bladder.

Rather than a scale, Zelman suggests taking out a tape measure and literally measuring your success. Measure your waist, thighs and arms. Are the inches changing even as the weight remains the same? "You may see that you are not losing weight because you are building muscle, and muscle weighs more than fat. But you are leaner," Zelman says.

Another way to keep your spirits up during a plateau and throughout the weight-loss process is to have a buddy. No matter how motivated you are when you start a new regimen, you should have someone there to keep you from becoming discouraged, because when we get down, we tend to return to our bad eating and training habits, says Zelman.

Keeping a journal is also a good strategy. "When you write everything down, it keeps you in touch with what you are doing," Zelman says. You should write down what you're eating at every meal and what you did during your workout. A journal is also a good place to express your frustrations to yourself, and also to give yourself some positive reinforcement. You can look back and follow your own accomplishments and refer to it if another plateau comes along.

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