3 Key Numbers That Lead to an Obesity Diagnosis

Obesity is more prevalent than ever in the United States. In fact according to the Centers for Disease Control and Prevention (CDC), about 40 percent of Americans are obese.

We know that obesity is linked to serious health risks, including heart disease, stroke, pregnancy complications, osteoarthritis and type 2 diabetes, per the National Institute of Diabetes and Digestive and Kidney Diseases. "Also, obesity results in an increased risk of mental illness, including anxiety and depression," says McKenzie Flinchum, RD, LDN, CPT, a CrossFit Games athlete and owner of The Flexible Dietician in Vero Beach, Florida.

But how exactly is obesity diagnosed, and what percent body fat is considered obese?

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Read more: The Long-Term Effects of Obesity on Health

While the causes of obesity are somewhat complicated — an unhealthy lifestyle can cause someone to become obese, but genetic factors also play a role, per the CDC — identifying the disease is a bit more straightforward. There are several measures that can determine whether or not someone is clinically obese.

BMI

A crude measure of obesity is a person's body mass index (BMI), which is his or her weight (in kilograms) divided by height (in meters) squared. According to the World Health Organization, a person with a BMI of 30 or more is generally considered obese. The major drawback to relying on this measure is the equation's inability to take muscle mass or frame size into account.

Read more: Why BMI Isn't Always the Best Measure of Body Composition — and What to Use Instead

Waist Circumference

According to the Obesity Medicine Association, the circumference of one's abdomen at the largest point "is a measurement of central adiposity and correlates well with metabolic disease risk." The measurements indicative of obesity are: 40 inches or greater for Caucasian males; 35 inches or greater for Caucasian females and Asian males; and 31 inches or greater for Asian females, per the Obesity Medical Association. Of course, this determination is reliant on an accurate measurement.

Body Fat Percentage

This is the most accurate means of assessing obesity, as this kind of body composition testing takes frame size, muscle mass, sex and age into account. However, according to the Obesity Medical Association, it "is more limited in assessing for metabolic disease risk than abdominal circumference."

It is quite difficult to determine your body fat percentage accurately at home, but testing is available in clinical and professional settings. Per the Obesity Medical Association:

• Males: 25 percent or higher body fat indicates obesity
• Females: 32 percent or higher indicates obesity

Read more: How to Estimate Your Body Fat Percentage

If you want to avoid becoming obese, your best bet is to be proactive. Eating a healthy diet — avoiding processed foods, relying on fiber- and nutrient-rich options instead — is an obvious first step. Becoming less sedentary will help as well. According to the American College of Sports Medicine, a person trying to prevent obesity will be most successful if he or she commits to at least 150 minutes of moderately intense exercise per week.

Those who are already obese can definitely see health benefits from starting a fitness plan. However, people who are obese have special considerations when exercising. For instance, they have an increased risk of orthopedic injury when participating in activities that put pressure on joints, muscles and connective tissue.

"A good place to start is to check with a doctor to determine if it is safe to begin exercise and to what extent," says Flinchum. "Once cleared for exercise, it is important to ease into new activities."

Flinchum recommends low-impact exercises, such as stationary biking, walking and swimming a few days per week: "Simply increasing movement is usually a great first step."

Read more: Want to Start Exercising for Weight Loss? This May Be the Perfect Gateway Workout