Keeping tabs on your size, weight, fat, or fitness? Get to know the pros and cons of common metrics.
As a data-driven society, we have a tendency to measure things to determine success. That’s especially true when it comes to our bodies, whether you step on the scale occasionally or track multiple body metrics on your phone each day.
But many common measurements may not be as accurate as we might believe. In fact, some could actually end up hurting us if we rely on them alone to assess our health, says Kelly Jones, R.D., a sports dietitian in Philadelphia.
Here are the pros and cons of five common body measurements, plus smarter ways to use each for your healthiest, fittest self.
Body Measurement #1: Your Clothing Size
Checking out how your clothes fit is one of the easiest ways to keep tabs on your body size. Notice your go-to pants suddenly feel tight? That might be a sign to evaluate your current food or exercise habits.
But fixating on wearing a particular size or item of clothing can be unnecessarily stressful. For one thing, there’s nothing standard about the number sewn to your top, pants, or dress.
“Different stores use different parameters for their sizes,” Jones says. You can walk into one store and see something listed as a size 8, she adds. Then you can walk into another store, and something that is actually the same size may be listed as a size 12.
The best way to use it: Focus on how your clothes fit and feel, rather than the size. You should feel comfortable and confident to go about your day.
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Body Measurement #2: Your Weight
The beauty of the humble scale is its accessibility. Many of us already have one at home, and if not, it’s easy to find one at a decent price. Plus, it’s simple to use: Disrobe, step on, see the number.
The problem with the scale: It’s not going to tell you the whole picture when it comes to your body composition. “The scale doesn’t account for muscle, fat, bone density, or even hydration, which can fluctuate throughout the day,” Jones says.
Over the long term, understanding your body composition becomes more important. That’s because metabolism slows down with age, and people tend to lose muscle and gain fat—making us weaker and less healthy.
Similarly, staying properly hydrated is vital for older adults. When your body is low on water, all your body’s systems must work harder to function properly. This can lead to fatigue, dizziness, or even a trip to the emergency room.
The best way to use it: Don’t get hung up on an exact number on the scale. Instead, think of your results in terms of range. If you’re trying to maintain a healthy weight, are you in your usual range, give or take a couple pounds? If you’re trying to lose weight, is the needle moving in the right direction over the span of a few weeks?
Your scale can also tell you if you’ve lost weight unintentionally, which can be a sign of diabetes or another health issue. If that’s the case, make an appointment with your doctor, especially if you have other symptoms.
Body Measurement #3: Your Muscle Mass
As you get older, gauging your muscle mass becomes more important, Jones says. Lean muscle has been linked with better health and increased longevity.
In fact, preserving or building lean muscle with strength training leads to some amazing health benefits: better metabolism, healthier joints, and even protection against harsh side effects of cancer treatment. And that’s just to name a few.
The gold standard for measuring muscle mass is something called dual-energy x-ray absorptiometry, or a DEXA scan, Jones says. If you’ve ever been tested for osteoporosis, you might recognize the name. DEXA is a common test to measure bone mass, but it also gives you a breakdown of muscle and fat mass.
Another common test is bioelectrical impedance analysis, which sends low-level electrical currents through the body to measure muscle and fat. And a simple grip strength test is a cheap, fast, and noninvasive way to get clues about your total-body strength.
The best way to use it: Ask your doctor the best way to measure your muscle mass or strength. For women 50 and older, or anyone who has previously broken a bone, also ask your doctor about your osteoporosis risk. Muscle mass and bone mass are different—but they are related in many ways when it comes to your health.
And if you don’t strength train regularly, add it your routine ASAP to protect your muscles and bones. Get started with our beginner’s guide to strength training.
Body Measurement #4: Your Body Mass Index
Your body mass index (BMI) is a calculation based on your weight and your height. In other words, it relates how much you weigh to how tall you are. You’re considered to be:
- Underweight: BMI is less than 18.5
- Normal weight: BMI is 18.5 to 24.9
- Overweight: BMI is 25.0 to 29.9
- Obese: BMI is 30.0 or greater
BMI is a number you can calculate yourself with online tools, such as this one from the Centers for Disease Control and Prevention. It’s also a number that your doctor might record at appointments. Research has shown high BMI can indicate a greater risk of serious health problems, including heart disease or diabetes.
Where BMI falls short: It’s slightly more nuanced than weight alone, but it still leaves out important information. “It doesn’t account for your body composition—your muscle versus your fat or even bone mass,” Jones says. “It also doesn’t account for gender, genetics, or age.”
In one University of California–Los Angeles (UCLA) study, researchers concluded that BMI is not a reliable way of measuring someone’s health. Roughly half of those considered overweight based on their BMI, for example, were actually healthy. And more than 30 percent of people with BMIs in the normal range were actually unhealthy.
What’s more, a meta-analysis of 32 studies that looked at the relationship between BMI and mortality rates found mortality rates for adults over 65 didn’t significantly increase until BMI reached 37. However, when BMI dipped to 20 or below, mortality rates for this age group increased. The sweet spot for older adults was a BMI of 27 to 27.9. The findings were published in the American Journal of Clinical Nutrition.
The best way to use it: Consider your BMI as one health metric to discuss with your doctor, along with other standard measurements like blood pressure or test results. Ask, “Am I at a healthy weight? Am I at risk of any health conditions?”
Body Measurement #5: Your Waistline
When the UCLA doctors started to dig into the nuances of their BMI findings, they discovered that where body fat was stored mattered. And all red flags pointed to the body’s midsection.
They weren’t the only scientists to zero in on our middles. A Nurses’ Health Study looked at the relationship between waist size and causes of death in middle age. Waist sizes of 35 inches or higher (measured around the top of the hip bones) put women at nearly double the risk of dying from heart disease, compared to women with a 28-inch waist or smaller.
The risks were similar when they looked at cancer and other causes of death. For men, red flags go up when waistlines reach 40 inches.
The American Heart Association (AHA) notes that body fat stored at the waistline is more “metabolically active” than fat stored on your thighs, chest, or upper arms.
The best way to use it: The AHA and World Health Organization (WHO) recommend calculating your waist-to-hip ratio.
- Start by measuring your waist.
- Next, find your hip circumference (measure around the largest part of your hips and buttocks).
- Divide your waist size by your hip size.
- This is your waist-to-hip ratio.
According to The WHO, a healthy waist-to-hip ration is:
- 0.85 or less for women
- 0.9 or less for men
Share your results with your health care provider and discuss what your results mean for you based on other key body measurements, your personal and family health history, and your lifestyle.
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