Despite the stigma around weight gain, obesity can be caused by many things beyond how much you eat or exercise. Genetics, social or economic factors, and certain medications or health conditions can also play a role.

Obesity is defined as an increase in the size and amount of fat cells in the body. This is determined by your body mass index (BMI).

Though having a high BMI does not necessarily indicate that a person is experiencing — or will experience — adverse health events, obesity can increase the risk of developing other health issues over time.

To calculate your BMI, you need to account for your height and weight, as well as your age and sex assigned at birth.

However, generally speaking, BMI is classified as follows, according to the Centers for Disease Control and Prevention (CDC):

< 18.5underweight
18.5–24.9average weight

This article looks closely at some facts about obesity and its causes.

Obesity trends in the United States can be summarized as follows:


  • As of 2022, all 50 states have an obesity rate of over 20%. Currently, 17 states have an obesity rate of over 35%.
  • The South has the highest prevalence of obesity (36.3%), followed by the Midwest (35.4%), the Northeast (29.9%), and the West (28.7%).
  • Washington, D.C., has the lowest rate of obesity, at just 24.7%. This is followed by Hawaii and Colorado at 25% and 25.1%, respectively.

Obesity in adults

  • It’s estimated that a little over 42% of American adults have obesity, while about 30.7% are overweight. Overall, more than two-thirds of U.S. adults in the United States are overweight or have obesity.
  • Adults between ages of 40 and 59 are more likely to have obesity. In fact, more than 44% of adults between these ages have obesity. Meanwhile, obesity affects 39.8% of adults ages 20 to 39 and 41.5% of adults above age 60.

Obesity in children and adolescents

  • Nearly 20% of children ages 2 to 19 in the United States also have obesity, which is more than 14.7 million children and adolescents.
  • Additionally, 1 in 8 preschoolers have obesity. However, the CDC reports that obesity rates among preschool children have fallen in recent years.
  • Children who are overweight or have obesity are five times more likely to have obesity or develop overweight as adults. This can increase their risk of many chronic diseases and health complications.

Many social factors are also associated with an increased risk of obesity. Economic stability, social support, access to healthcare, education, safe housing, and transportation can all contribute to health disparities. They may have a significant impact on overall well-being and quality of life.

For example, living or working in economically disadvantaged areas or communities can mean having limited access to affordable ways to stay fit. Moreover, living in an area with limited access to affordable and nutritious foods — also known as a “food desert” — can increase the risk of obesity by up to 30%.

This disproportionally affects certain historically marginalized groups. According to the CDC, about 49.9% of non-Hispanic Black adults have obesity. This is followed by Hispanic people at 45.6%, non-Hispanic white people at 41.4%, and non-Hispanic Asian individuals at 16.1%.


The estimated annual medical cost of obesity in the United States is $173 billion annually in 2019 dollars. People living with obesity are often forced to pay more out of pocket for medical care than those who do not have the condition.

In fact, the medical costs for people living with obesity are $1,861 higher yearly than for those within the recommended BMI range for their height and weight. Other research indicates an even higher figure of $2,505.

That being said, the cost of obesity cannot be so easily summed up by one figure. In the United States, overall healthcare costs are much higher than in many other countries.

According to data from the Organisation for Economic Co-operation and Development (OECD), Americans have the third highest out-of-pocket spending on healthcare. Malta and Switzerland are the only countries where out-of-pocket spending is higher.

In addition, how much you spend on healthcare also depends on whether you have health insurance and the type of coverage you have. There are significant inequities in access to health insurance for historically marginalized groups.

Research shows that the gap in coverage between Latinx/Hispanic people or Black people and people who are white has been falling in recent years. However, more people in these groups are still uninsured compared with people who are white.

Living in a low income household can also make it harder for a person to access or pay for health insurance — especially for employer-based plans.

Research shows that historically marginalized groups living in low income households have 68% fewer odds of having health insurance than people who are white, have no or limited health issues, and live in higher income households.

Though living with obesity does not necessarily indicate that you’re experiencing or will experience adverse health events, obesity can increase your risk of several chronic conditions.

These include heart disease, type 2 diabetes, and cancer. Obesity may also be associated with reduced quality of life, including poorer mental well-being. This may have to do with the social stigma that still exists and the discrimination that some people may face as a result.

One study involving over 10,000 adults found that a higher waist circumference, waist-to-height ratio, and BMI were all associated with a higher risk of type 2 diabetes.

Additionally, the study found that those with the greatest increases in body weight or waist circumference over an average of 2.8 years had an approximately 1.5- and 1.4-fold greater risk of developing type 2 diabetes, respectively.

The number of calories people in North America and Europe consume has been rising since 2000, equaling about 3,540 per day in 2021, according to the United Nations (UN).

When the number of calories you consume is greater than the number of calories your body burns, your body stores the extra energy as fat, which can contribute to weight gain over time.

However, the number of calories you consume does not always serve as the only possible cause for weight gain. The quality of the food you eat matters just as much, if not more.

Many modern foods are processed, containing an excess of ingredients like sodium, fat, and sugar. They often contain more calories than needed and are easier to digest, which can contribute to weight gain.

In addition, eating foods high in refined starch and sugar can raise your insulin, which can make you hungrier, causing you to eat more.

Many processed foods also often contain artificial ingredients whose impact on health has not been adequately tested.

The idea that what a person eats and how much they exercise are the primary influencers of their weight is a complex stigma that can be damaging because it wrongfully implies that obesity is a sign of moral failure.

In reality, many factors can contribute to weight gain and obesity. This can include how well you sleep, what medications you take, what other medical conditions you may have, and your genetics.

For example, variations in certain genes can influence hunger and appetite, leading to increased food intake. Another example is Cushing syndrome, which is a condition that can cause weight gain due to the body oversecreting the hormone cortisol.

The prevalence of obesity in the United States is 42%, which means it’s extremely common. However, having a high BMI is not always a sign that a person is experiencing or will experience adverse health events.

A person’s weight can be a simple reflection of their genetics. Medical conditions, medications, and food ingredients can also contribute to a person’s weight.

In addition, social and healthcare inequities often make it harder for people from historically marginalized groups to access nutritious food, quality medical care, and health insurance coverage.

Despite the stigma that still exists around obesity, it is a complex condition that cannot always be attributed to any one particular cause.