THIS is the best way to tell if you're at a healthy weight

You lift weights, eat healthy foods, and fit into your jeans. So why the hell is your doctor telling you that youre at an unhealthy weight according to the body mass index (BMI)?

Welp, BMI, once the gold standard for assessing a person's weight—and overall longevity—has fallen out of favor. And if you're trying to lose weight, having a BMI in the overweight or obesity range, even if you're doing everything right, can be a huge downer.

So we're here to tell you that your BMI calculation officially means nothing.

We've asked experts for the biggest reasons why your BMI is totally off base and the best way to get a feel for how your health measures up.

1. IT'S ANCIENT.

"BMI was created about 200 years ago as a way to estimate obesity," says Leslie Cho, M.D., director of the Cleveland Clinic Women's Cardiovascular Center. But it doesn't actually measure the fat on your frame. It's literally a weight-to-height ratio, considering no other factors (sex, bone density, race).

2. IT CONFUSES FIT WITH FAT.

Athlete? Have a lot of lean-muscle mass? You could still have a BMI that qualifies as overweight or obese, even though you may be in great shape. According to a 2016 study, 47 percent of people in the overweight BMI category—along with 29 percent classified as obese—are actually healthy.

3. IT CAN'T FULLY MEASURE HEALTH.

On the flip side, the same study also found that more than 30 percent of people with so-called healthy BMIs have too-high blood pressure, cholesterol, inflammation levels, or insulin resistance, the hallmark of Type 2 diabetes. Those are all truer tests of your actual wellness. (Kick-start your new, healthy routine with Women's Health's 12-Week Total-Body Transformation!)

The bottom line: Waist circumference is a far better gauge of your health. It may not consider things like ethnicity either, but excessive abdominal fat is a universal red flag. For women, measurements of 35 inches or more (around the top of the hip bones) are consistently linked with an increased risk for chronic disease. And if you're going to step on the scale, choose one that calculates full body composition—i.e., your lean and fat mass. (Try Withings Body, $100, withings.com.)

This article originally appeared in the May 2017 issue of Women's Health. For more great advice, pick up a copy of the issue on newsstands now!