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The Metrics of Health Change: Four Numbers You Need to Know

You resolve to develop healthier habits. Here are the metrics that measure your success.

Hiroshi Watanabe/Getty Images
Hiroshi Watanabe/Getty Images,

by Sarah Mahoney

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You can’t manage what you can’t measure, the saying goes, and that’s especially true for people trying to change their health. “I feel better these days” or “I think I’m doing OK,” don’t say nearly as much about your health as your blood pressure or weight does. In fact, experts say knowing just four numbers—all the time—can help you be the master of your own health destiny.

1. Body mass index (BMI). The BMI is a simple calculation based on the ratio of height to weight, yet it’s considered one of the most valuable health metrics, identifying potential risks of diseases ranging from diabetes and heart problems to arthritis and depression. “It’s not a perfect measure,” says Laila Tabatabai, M.D., an endocrinologist at Houston Methodist. It doesn’t differentiate between muscle mass and fat, so some of the world’s top athletes get incorrectly tagged as obese. But if you’re not Shaquille O’Neal or Sammy Sosa, it’s the best thing we’ve got. “And it’s a lot easier than getting a body-fat calculation,” she says.

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While most of us can get wrapped up “in the difference between vanity pounds and health pounds, I like to see people get close to 25, and as far down as 20. But when I see it above 27, I really get on top of them to start losing weight in a gradual manner. They are at an elevated risk for hypertension and other problems.” You can calculate your BMI here.

Your goal: A BMI between 18.5 and 25. Anything between 25 and 29.9 is considered overweight, and 30 and above is obese. Going lower than 18.5 puts people at risk for bone loss and certain immune problems.

2. Blood pressure. “About 80 million people in the U.S. have high blood pressure, and we have great medications to control it,” says Mary Ann Bauman, M.D., the medical director for women's health at Integris Health in Oklahoma City, “spokesperson for the American Heart Association. “Yet only 54 percent have it well under control, despite the fact that we’ve had good medications for more than 50 years.” If you’ve been warned about your blood pressure, you’re likely keeping an eye on it. If not, you should know that anything higher than 120/80 mmHg (millimeters of mercury) vaults you into the danger zone. If the higher number is between 120 and 139, and the lower between 80 and 89, doctors consider that pre-hypertension. Go higher and you’re facing elevated risks for a variety of heart problems, as well as stroke. (Read more about the categories of hypertension here.)

Wondering about the difference between the upper and lower numbers? The first is systolicblood pressure, which measures the blood flow in arteries when the heart beats or contracts. The second, diastolic, measures the blood flow between beats, when the heart is relaxing. If you don’t own a BP cuff, use the ones you find in drugstores and supermarkets, says Bauman. “They may or may not be as accurate as those you use at home, but it’s still better than not knowing your blood pressure.”

Your goal: 120/80 mmHg

3. Cholesterol. A straightforward way to keep on eye on this, says Bauman, is to look for a total cholesterol level of less than 200, based on a blood sample taken after fasting overnight. The score is calculated this way: HDL (the good, or “happy,” cholesterol) + LDL (the bad, or “lousy,” kind) + 20 percent of your triglyceride level. If your combined number is less than 180, which she says is ideal, don’t be surprised if your doctor doesn’t even insist on an annual test.

But if your combined number is higher than 200, you’ll have to dig a little deeper into the components. The latest thinking is that LDL number is not the only focus, “and the American College of Cardiology has done away with target numbers after finding some cardiac risks were mismanaged,” says Tabatabai. Some higher levels are fine, as long as the HDL levels are higher, too. “It is very complicated,” she says, “and lots of people will have their cholesterol checked at a health fair and just get the total number, without understanding each of the scores.”

HDL stands for high-density lipoprotein, and you want to have higher levels of this type, since it lowers the risk of coronary disease. LDL stands for low-density lipoprotein, and is a type of cholesterol that you want to be low, since too much is linked to higher heart disease rates. Triglycerides are a type of fat in the blood, with some created by our bodies, and some from the foods we eat. And as with LDL, a lower score here is better.

Your Goal: A combined number of less than 200, and talk to your doctor

4. Blood glucose. This test measures the amount of sugar in the blood, which lets doctors assess your risk of developing diabetes, which increases with age. Tabatabai suggests an annual A1C test, “which measures the amount of glucose that sticks to the red blood cells over the past two to three months.” As a result, she says, “you can’t cheat the test the way you can the fasting plasma glucose, which measures sugar at one point in time.” A reading of less than 5.7 percent is considered normal, while 5.7 to 6.4 percent is considered pre-diabetic. Anything higher results in a diagnosis of diabetes.

In the older fasting plasma glucose (FBG) test, anything less than 100 is normal, from 100 to 125 indicates pre-diabetes and 126 or higher diabetes. (Bauman says she typically goes for the FPG test first, “depending on my index of suspicion,” because it’s cheaper.)

No matter which test is used, experts are adamant that knowing this number can allow you to make powerful changes. “If you catch this in the pre-diabetes range, you really can turn back the clock,” says Tabatabai.

Your Goal: 5.7 percent or less on an AIC test, or below 100 with the FPG test

“About 80 million people in the U.S. have high blood pressure, and we have great medications to control it.”

Four Signs That You’re Getting Healthier

These four indices should be measured at least once a year, says Bauman, and if you have an issue, you might need to be monitored more frequently.

Beyond the big four, experts have a few other numbers that can make benchmarking health changes in your life easier:

1. You’re getting 150 minutes of moderate activity per week.

2. You’re consuming 1,500 milligrams of sodium or less each day. Bauman says that may take some work, given that the average American eats 4,000 a day, much of it from baked goods, soup, pizza, lunchmeat and pickles.

3. You eat no more than 6 teaspoons of sugar (women) or 9 teaspoons (men). Sugar has been linked to a growing number of health issues.

4. You serve yourself 5 to 9 servings of produce each day. But be careful, says Tabatabai, “because it depends on what you’re eating with the produce.” If cheese, cream sauces and fatty salad dressings are part of your produce plan, you’re likely negating the benefits of fruits and vegetables.

See also: Weight-Loss Guidelines That Really Work