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) Here’s how the BMI ranges are categorized:
Underweight is a BMI less than 18.5Normal weight is a BMI between 18.5 and 24.9Overweight is a BMI of 25 to 29.9Obesity is a BMI of 30 or greater
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. He recommends recording your food or calorie intake for a few days to understand what your eating habits are truly like. “Many patients will come back and say, ‘I never knew how much I ate,’” he explains. It may be the reality check you need to change your habits. Use whatever method you feel most comfortable with, whether that’s writing it in a journal or using an app on your smartphone. A study found that the more frequently participants used a web app to track their diet habits over six months, the more weight they lost. (6)
4. Know How Much You Move
As with monitoring your food intake, you’ve got to know what your physical activity level is like. At the Weight Management Center at MUSC, everyone who joins the program gets a Fitbit activity tracker, which makes it easy to track and record your exercise and everyday movements. (Walking up the stairs counts!) Even if you’re not in a program, there are tons of apps at your disposal, whether you’re on an Android or an iPhone, and fitness trackers you can wear on your wrist.
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. 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)
