You’ve long heard doctors talk about BMI — or body mass index — and you may even know yours off the top of your head, especially if you were told your number was in the unhealthy range.
Technically, your BMI is used “as a good — though rough — indicator of how much fat mass you’re likely to have,” says Patrick M. O’Neil, PhD, the director of the weight management center at the Medical University of South Carolina (MUSC) and a professor in the department of psychiatry and behavioral sciences.
You can calculate your BMI by dividing your weight in pounds by your height in inches squared, and then multiplying that number by 703. You can use this equation to get your number: weight (lb) / [height (in) x height (in)] x 703, according to the Centers for Disease Control and Prevention (CDC). (1)
While there’s a lot being said about how being overweight or obese is bad for health, it’s not the full picture. “If we were being more precise, we’d say excess body fat is bad for your health,” says Dr. O’Neil. Excess body fat, especially visceral fat (the kind that coats the insides of the body and accumulates on internal organs), is linked to higher blood pressure, blood sugar levels, and cholesterol, all of which can affect your risk for conditions like type 2 diabetes and heart disease. (3) BMI is only a correlation of that, since usually the higher the BMI number, the more fat you’re likely to be carrying around.
That said, BMI has its limitations for what it can and can’t tell you about your health and whether you need to lose weight. As the CDC points out, age, sex, ethnicity, and muscle mass can skew BMI as it relates to body fat. (4) For instance, if you’re extremely athletic and have a lot of muscle mass, your BMI may indicate that you’re obese when you’re actually fit. “With BMI, you can’t say that it offers conclusive proof that someone has excess body fat,” adds O’Neil.
That said, if your BMI is in the higher range and your waist circumference also indicates you’re at risk for health problems, your doctor may advise you to lose weight, which will likely lower your BMI. The CDC’s recommended waist circumference guidelines: less than 35 inches for a woman (nonpregnant) and less than 40 inches for a man.
Here are the science- and expert-backed steps that will help you achieve lasting results.
1. Get an Accurate Reading of Your Personal BMI
Online BMI calculators abound, but you should get your official BMI reading at your doctor’s office from someone who is weighing you and measuring your height. “If you ask most of us how much we weigh, we’ll report we weigh less than we do, and we’ll say we’re a little taller. That would lead to an underestimation,” says O’Neil.
2. Set a Realistic Goal if You’re Trying to Lower Your BMI
Losing as little as 5 to 10 percent of your body weight can have substantial health benefits, according to the CDC. (5) For some people, this means that your BMI still may be in the overweight range, and that may be okay.
“It’s unrealistic and unnecessary for everyone with a BMI of 30 or more to get to a BMI in the normal range. The health significance of BMI is not indicated by the number it is today, but if today’s BMI is more or less than it was in the past,” says O’Neil. In other words, it’s all about whether you’re making strides toward a better health future. Your goal should be to lose a modest amount of weight and then reevaluate your progress.
5. Weigh Yourself Regularly to Figure Out What’s Working (and What Isn’t)
Once a week, get on the scale. Then chart your weight (this is easy to do via an app, or you can DIY using a graph, like the one from MUSC). (7) This way, you’ll know whether you need to change up your weight loss approach — or stay the course.
6. Now Get Moving With a Workout of Your Choice
If you know you need to start exercising more — and your activity log proves it — you’re going to want to exercise. That doesn’t necessarily mean jumping into kickboxing or trying out CrossFit.
“I tell patients that you don’t get extra credit for doing the toughest exercise you can find,” says O’Neil. He suggests picking an activity that you find fun or tolerable, such as walking your dog or hiking, and making that your regular workout.
7. Set Workout Targets So You’re More Likely to Stay on Track
It’s not enough to say that you’re going to start exercising “more.” Rather, plan it out.
Commit to walking for 20 minutes three times this week, and plan the days you’re going to do it and what time — for instance after work on Mondays, Wednesdays, and Fridays. And if something comes up, know that you can shorten it to 5 or 10 minutes — everything counts.
“First, establish the habit of doing an activity, and then focus on the duration and intensity of it,” advises O’Neil.
8. Clean Up Your Eating to Make Sure Your Diet Is Working for You
When you want to lose weight, there’s no shortage of diet advice. What’s more, research shows that focusing on both diet and exercise is the best combination for successfully losing weight. (8)
But because diets are so variable depending on the person — your coworker may swear by low-carb eating while that would make you miserable — research suggests that the quality of your food may matter more.
For instance, a study found that foods like potato chips, processed meats, red meat, and sugary beverages were associated with weight gain, while those like fruits, veggies, whole grains, nuts, and yogurt were associated with weight loss. (9)
9. Stay Consistent, Even if You Aren’t Seeing Results Right Away
Even if the weight doesn’t seem like it’s coming off fast enough, stay the course. It’s only with consistent efforts to eat well, move more, and maintain other healthy habits that affect weight (like getting enough sleep) that the pounds come off permanently, research suggests. (10) Researchers found that when weight jumped up and down — possibly because of inconsistent efforts — people were more likely to give up on their goals. Remember: You’ve got this.