Q: I started a weight loss program 2 weeks ago, but the scale hasn't budged. Why?

A: It's not uncommon for people to lose weight at different rates, even if their eating and exercise habits are the same. The most likely explanation is fluid retention, says Franca Alphin, MPH, RD, nutrition director of student health services at Duke University Medical Center in Durham, NC. Some people are just more prone to retaining fluids.

To prevent this, watch your salt intake, drink more water, and be patient. Come next week, you may suddenly drop the few pounds you were hanging on to as your body starts adjusting to your new regimen, Alphin says.

However, if you don't see a change by the fourth week, reevaluate what you're doing. If you started walking, great, but realize that, at most, you'll be burning about 100 calories for each mile walked. Since there are 3,500 calories in 1 lb of fat, you'll get faster results by also trimming some calories. Most people can expect to lose an average of 1 to 2 lb a week. (If you have 10 lb or less to lose, the weight will come off more slowly: about 1/4 to 1/2 lb a week.