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By Madelyn Fernstrom, PhD

Until about 30 years ago, there was no “official” standard for what a healthy body weight should be.

It was only when Body Mass Index became the first nationally-accepted standard that the public learned about obesity. In fact, calculating BMI (based off an individual’s weight and height) was the first way Americans could “measure” obesity, instead of simply hearing from a physician that “you need to lose weight.”

Consequently, there’s been almost an obsession with the numbers, especially as a lot of scientific research has focused on how BMI and disease risk are related. But it can be discouraging, for example, if you’re a 5-foot-4-inch woman weighing 160 pounds who works out regularly and eats healthy. According to the BMI, you’re in a range that’s considered “overweight."

That begs the question: Does your weight really matter?

In short, your weight (and BMI) does matter — but only as part of your overall personal evaluation. It’s not the only factor. And like most measures of health, BMI is not perfect. For example, results can be thrown off if you have a higher muscle mass, greater bone density or are pregnant.

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And while BMI is one important index of disease risk, it’s not the only one. Those with a BMI modestly above 25 may not have additional risk. And their blood work (like cholesterol and glucose) and blood pressure can be totally normal, often a reflection of a positive lifestyle, including healthy eating and increased physical activity. On the flip side, it’s been estimated that up to a third of people with a “healthy” BMI have an increased health risk, when looking at these same factors.

Here are some other factors you need to think about (and can measure):

-Your muscle and body fat percentages

-Your waist circumference

-Your waist-to-hip ratio

-Your fitness level

-Your blood work (like cholesterol, glucose, liver function tests)

-Your blood pressure

-Your family history

Take all of these health factors — including weight — into account when figuring out a realistic target weight and how to achieve it. The good news is that a healthy lifestyle (eating, activity, stress management, sleep) can often improve your health, even without losing weight.

In partnership with your doctor, you might find that a weight (and BMI) suggesting increased risk does not automatically translate to a major weight loss effort. Sometimes the best path is “just don’t gain.” Keeping your weight stable takes effort — and is often a more productive approach to avoiding the dreaded “weight creep” with age!

Madelyn Fernstrom, PhD is the NBC News Health Editor. Follow her on Twitter @drfernstrom.