How to get off weight-loss plateau

Q. I started exercising and began to lose weight but now the scale won't budge, even though I'm still exercising. What's wrong?

A. When you started exercising you burned more calories that you were eating, so your body met its additional needs by burning body fat and you lost weight. But at a lower weight, you burn fewer calories in all your daily activities.

You may have stopped losing weight because you are now burning about as much as you are eating. To continue losing weight, you must once again burn more than you eat; to do so you can further increase your exercise or cut back a little more on what you eat. First, however, review all the diet and exercise changes you've made since you started losing weight and see how your current habits stack up. Sometimes new habits gradually slip a little -- not enough to cause weight gain, but enough to keep you stuck on a plateau.

There is also the possibility that your weight may settle at a level that is healthy but not as low as you'd like. Although excess weight is linked with increased risk of certain cancers and other health problems, there is a wide range of healthy weights.

Your healthy weight may not match the super-thin look so popular in the fashion and entertainment worlds.

Q. If a food or supplement supplies 100 percent of Daily Value for a nutrient, is that the same as 100 percent of the RDA?

A. No. The "daily value" (DV) of a nutrient is meant to approximate the amount we might find in the healthy diet of an average adult, but many of the values were set up based on an earlier set of recommended dietary allowances (RDA).

DV figures for fats, carbohydrate, fiber and protein are based on a 2,000 calorie diet for an average adult, and planners intended individuals to adjust those numbers if their calorie needs differ. For other nutrients, there is only one DV, despite different RDAs reflecting needs that differ based on age and gender.

For example, one or more foods that total 100 percent of DV for vitamin C provide 60 milligrams (mg), although the RDA for adults is now 75-90 mg. On the other hand, 100 percent of DV for iron is actually more than double the RDA for adult men and women over age 50.

Use the "% Daily Value" figures to compare different food options and to identify roughly whether a food is high or low in a particular nutrient. If a serving of a food supplies 20 percent or more of daily value, regardless of what percent of your personal needs this is, the food is relatively high in that nutrient. If a serving supplies 5 percent or less of daily value, it is not considered a significant source.

Q. Why is there a lower limit set for a healthy body mass index (BMI)? Isn't the lowest possible weight the healthiest?

A. Excess weight raises risk of cancer, diabetes and heart disease, but weight that is too low can be unhealthy also. Severely restricted eating, associated with a BMI less than 18.5, usually means that nutritional needs are not met. Weight this low is also tied to eating disorders.

In some cases, excessively low weight may not cause poor health, but may be a sign of poor health, as in some respiratory and other chronic illnesses. Studies consistently link low BMI with osteoporosis and low bone mineral density. Examples of low weights associated with unhealthy BMIs are someone who is 5 feet 5 inches tall and weighs 105 pounds or less, and someone who is 5 feet 9 inches tall and weighs 120 pounds or less.

Note that standard cutoffs defining healthy and unhealthy BMIs do not apply to children, teenagers, athletes, and pregnant women.

Karen Collins, registered dietitian, writes this column for the American Institute for Cancer Research.Collins has a master of science in human nutrition. To submit a question, please write to Ask the Nutritionist, c/o the Daily Herald, 1759 R St.,N.W.,Washington, D.C. 20009.Questions will not be responded to personally.