Obesity: What You Need to Know

Obesity is a chronic disease that is diagnosed when a person’s body weight is about what’s considered healthy for their height. Obesity, defined by an oft-controversial metric of body mass index (BMI) above 30 for adults, is associated with health risks including cardiovascular disease, diabetes, and metabolic conditions.

However, some people with obesity are metabolically healthy and don’t have this increased risk for disease, just as some people who are not overweight still suffer from these diseases. 

Continue reading to learn more, including classes of BMI and why your BMI doesn’t tell you everything you need to know about your health. 

What Is Obesity, and How Is It Calculated?

Obesity is calculated by comparing a person's weight to their height. This is a calculation known as the body mass index. For adults, obesity is diagnosed when BMI is 30 or higher. That means for a male who is 5 feet, nine inches tall (the average male height), weighing 203 pounds or more qualifies him as obese. 

Although the use of BMI is widespread in modern medicine, it is a problematic and overly simplistic metric. BMI ranges were initially determined based on measurements of northern European white men in the 1800s. Thus, the data do not reflect modern life. It also ignores sex, gender, ethnicity, socioeconomic status, and other important factors.

In addition, the measurement does not consider a person’s body composition, including whether they have lots of muscle. For that reason, athletes often have a high, sometimes even obese, BMI.

Obesity Classes

The Centers for Disease Control and Prevention (CDC) breaks down adult obesity into three subclasses. They are:

• Class 1: BMI of 30–35
• Class 2: BMI of 35–40 
• Class 3: BMI of 40 or higher

Class 3 obesity is sometimes categorized as severe obesity, which used to be known as morbid obesity. In recent years that term has been dropped to combat stigma around obesity. 

What Is Childhood Obesity?

Childhood obesity is diagnosed when a person’s BMI is at the 95th percentile or higher on growth charts for their age and sex. Just as with adults, the calculation of BMI is problematic for children, and athletes may have a high BMI due to their muscle mass compared with their peers.

What Are the Symptoms of Obesity?

There are no specific symptoms of obesity, because it is such a complex condition. About 7% people with obesity are metabolically healthy—that means their excess weight isn’t causing any health concerns. However, researchers have determined that obesity increases risks for certain health conditions.

What Are the Complications of Obesity?

Compared to people with a BMI in the healthy range, people with obesity are at increased risk of:

• Cardiovascular diseases, including coronary heart disease and stroke
• Type 2 diabetes
• High blood pressure
• Sleep apnea
• Breathing problem
• Joint problems and pain
• Certain cancers
• Gallbladder disease
• Fatty liver disease
• High cholesterol
• Mental health issues
• Arthritis
• Infertility and irregular menstrual cycles

While there are physical reasons for many of these complications, others are caused or worsened by how society treats people with obesity. Research shows that people with obesity get lower quality care from healthcare professionals when compared with people of lower weight. Stigma, judgment, and shame from family, colleagues, or self can also contribute to mental and emotional complications of obesity. 

What Causes Obesity?

The causes of obesity are incredibly varied and are about much more than simply the food you eat—although that can play a role. However, obesity is much more complex than the outdated idea of calories consumed vs. calories burned, and is not a personal failing or a reflection of your self-control. Many different factors contribute to the development of obesity, including:

• Food, activity, and sleep: A person’s eating patterns, movement, and sleep can all contribute to weight gain. 
• Genetic factors: Many different genes can contribute to obesity, and your genetics often impacts body size. 
• Social determinants of health: Where you live, work and learn can impact your risk for obesity. Socioeconomic factors, including access to quality fresh food, also play a role. 
• Illnesses and medications: Certain diseases and medications can lead to weight gain. 

Health Conditions That May Lead to Weight Gain

Some health conditions can contribute to weight gain, including:

• Polycystic ovary syndrome (PCOS)
• Metabolic syndrome
• Cushing syndrome
• Thyroid disease
• Prader-Willi syndrome

Medications, including those that treat depression and other mental health conditions, can also lead to weight gain. Treating these illnesses, or adjusting medications, may help manage obesity.

How Is Obesity Diagnosed?

Obesity is most often diagnosed using a person’s BMI. Since the BMI defines obesity, despite its flaws, this is the true diagnostic test.

However, there are other diagnostic criteria that a healthcare provider can use to determine whether the classification of obesity is impacting your health. These can give a better understanding of your body composition, and include:

• Measuring your waist circumference
• Calculating body fat, including by using a skinfold test
• Looking at labs that measure your blood sugar, cholesterol, liver function, and more
• Getting a physical exam and giving a thorough health history

How Is Obesity Treated?

Obesity is a complex disease, and treating it is difficult. While weight loss is often a goal for people with obesity, sustaining weight loss through dietary and lifestyle changes alone is challenging.

Fortunately, even a small amount of weight loss can make a difference. in fact, losing just 5% to 10% of your body weight can lead to more energy, better sleep, and lower blood sugars, even if you still have obesity.

To make lasting changes to your weight, the CDC recommends:

• Eat whole foods: Add more fruits and vegetables, while reducing processed foods and sugary beverages. 
• Move more: Aim for 150 minutes of moderate exercise, like walking, each week. Add in one or two days of strength training. 

Treatments for obesity can also include medical interventions, like weight loss surgery or weight loss drugs. While these options help many people, they’re not a magic pill. They come with their own serious side effects, which you should discuss with your healthcare provider if you are considering them. 

How Can You Prevent Obesity?

Focusing on health throughout your life may help prevent obesity. More importantly, it will help contribute to your overall health. Try these tips.

• Eat whole foods. 
• Limit processed foods.
• Get regular physical activity.
• Limit screen time.
• Find a healthcare provider or care provider who listens to your concerns and doesn’t stigmatize your weight.
• Treat underlying health concerns.
• Practice self care and body acceptance.
• Build your self confidence.
• Create supportive environments.

Summary

Obesity is a chronic condition that is diagnosed when a person’s BMI is 30 or higher. Having a BMI considered obese is associated with increased risk for adverse health effects, including cardiovascular disease and diabetes. However, some people with obesity are metabolically healthy.

Eating healthy, whole foods, exercising more and sleeping well may help you lose weight, but for most people treating obesity is much more complex than lifestyle changes. It can include surgical or medical interventions, as well as treating underlying health conditions.

Finding a trusted healthcare provider who does not stigmatize your weight can help you develop a treatment plan that works for you.