Using Body Mass Index (BMI) to measure your health outlook and set weight-loss goals.

Using Body Mass Index (BMI) to measure your health outlook and set weight-loss goals.

NEW! Excerpted from The EatingWell Diet Book.

Now that you've made a commitment to lose weight, it's time to take stock. What is your weight now, and how far is it from where you'd like it to be?

Many of us have an idea of what we'd like to weigh, and usually it's based on notions that are long on idealism and short on reality. If you're 45, it's probably not realistic to think you can get back to your high school weight. Trying to achieve fashion-model thinness is probably a waste of energy, too, since most top models are woefully underweight by any standard. So what is a sensible weight for you?

Rather than focusing on a single, arbitrary number of pounds, focus instead on finding a healthy weight range-that is, a weight that's associated with a longer, healthier life and lower risk of the diseases linked to being overweight (high blood pressure, stroke, heart disease, diabetes and others). Most experts determine healthy-weight ranges with a calculation that takes both weight and height into account to give you a single number called a Body Mass Index (BMI) value.

The BMI is a pretty reliable way to measure your health outlook; in general, the lower your BMI, the lower your risks of health problems related to your weight. But a BMI value doesn't give you the whole picture. For starters, it's not a reliable measurement for pregnant or breastfeeding women, who need to have larger fat stores to support a growing baby or to produce milk. The BMI is downright misleading for some bodybuilders or competitive athletes, too: since muscle is denser than fat, a well-muscled body may register as "obese" on the BMI scale.

For all these reasons, most experts also take a second measurement in addition to the BMI: waist size. Why the waist? Studies show that people who have more fat around their abdomens tend to have greater risks of problems like heart disease and diabetes-so knowing what the tape tells you about your waist circumference can help determine your overall health prognosis.

In general, health problems increase when a waist measurement-not your belt size, by the way-is greater than 40 inches for men and 35 inches for women. So, if your BMI puts you in a higher risk category, having a waist size above those numbers raises your level of risk even higher and adds to the list of reasons you would want to lose weight.

If your BMI is: Below 25

Your health risk profile is: Ideal. You probably don't need to lose weight for health reasons, though it might boost your self-esteem and confidence.

If your BMI is: 25 - 29.9

Your health risk profile is: Moderate. Your chance of developing heart disease, diabetes and other diseases associated with excess weight is higher, especially at the higher numbers in this range. Losing some weight can help you feel great now-and it can also prevent you from sliding into a higher risk category later on. Waist size over 40" (men) or 35" (women)? Your risk of health problems is increased, but weight loss can bring your numbers into a healthier range.

If your BMI is: 30 & Higher

Your health risk profile is: High risk. Officially categorized as "obese," you might already be facing some health issues related to your weight. But take heart: you'll see the most dramatic effects on your health and well-being as the weight comes off. Waist size over 40" (men) or 35" (women)? With the help of your doctor, make a commitment to lose some weight-your health and well-being depend on it.