Body mass index: Calculate it and learn from it

It's Jan. 1, the time many of us step away from the holiday treats and onto the scale. If you've put on a few pounds, you're not alone. According to the U.S. Department of Health and Human Services (HHS), Americans gain an average of one pound during the holiday season. While this seems small, HHS researchers warn that over time this extra weight can accumulate and contribute to obesity.

Holiday weight gain appears to be catching up with many Americans, including Arizonans. In 2010, the Centers for Disease Control and Prevention (CDC) reported that 24 percent of people living in Arizona were considered obese. The CDC also found that approximately one-third of U.S. adults - nearly 34 percent of the population - are obese. Among children ages 2-19, 17 percent qualify as obese.

Carrying around these extra pounds is dangerous to your health. It increases your risk for many chronic conditions and diseases, including:

• Cancer (breast, colon, gallbladder, prostate and others);

• Diabetes;

• High blood pressure;

• Osteoarthritis; and

• Sleep apnea.

How do you know if your weight is considered healthy or hazardous? Body mass index, or BMI, is one fairly reliable screening tool used to identify possible weight problems in adults and adolescents. To calculate your BMI, divide your weight in pounds by your height in inches squared. Once you have this number, multiply it by 703. Or, you can put away your calculator and visit the National Heart, Lung, and Blood Institute (NHLBI) website ( to use its BMI calculator. The site even has a free BMI calculator phone app for you to download.

Once you've calculated your BMI, here's what it means if you're an adult ages 20 or older:

• Less than 18.5: Underweight

• 18.5 - 24.9: Normal weight

• 25 - 29.9: Overweight

• 30 or more: Obese

There's a fairly strong relationship between the BMI number and body fat. However, age, gender and other factors can sometimes affect it. For example, at the same BMI, women tend to have more body fat than men. Also at the same BMI, older people, on average, have more body fat than younger adults. Highly trained athletes also may have a high BMI because of their muscle mass.

Although the method used to calculate BMI is the same for adults and adolescents, the way the BMI number is interpreted for children and teens is different. The amount of body fat changes with age and differs between girls and boys.

Knowing your BMI is a good step toward maintaining a healthy weight. It's also important to discuss your weight with your physician. Your doctor may recommend a healthy diet and exercise to help you get on the path to good health.