“Obesogenic” is a word coined in the last two decades.  It refers to an environment that promotes increased food intake, sugary and high-fat foods, and inactivity. The CDC reports that in 2018 in the United States, more than two in five adults ^[1] and one in five children were obese ^[2]. And the obesity rates of Americans continue to rise.

The health consequences of too much body fat are numerous, including increased risks for cardiovascular disease, type 2 diabetes, and some cancers. The medical costs related to obesity are enormous.   Obese people spend close to $1,500 more per year for medical care than people of a healthy weight.

Numerous obesogenic agents contribute to this immense public health problem and have become part of everyday life.  Some examples are listed below:

• The fast food industry has been growing for decades and continues to grow despite the latest economic slump.
  
• Food portions have been getting bigger since the 1960s. 
• During the 1990s, America experienced the “super-size” marketing boom, which still endures.
• Today,  very few people walk or ride bikes to work or school. 
• In the 1960s, walking and biking were common among all age groups.
  
• Escalators, elevators, and moving walkways dominate shopping malls and office buildings.
• Factory work has become increasingly mechanized and robotized.
  

The list of obesity-promoting factors goes on and on. They result from modernization, industrialization, and urbanization continuing without public health officials or government adequately addressing the concurrent rise in overweight and obesity.

Obesity Rates

Since 1960, the prevalence of overweight has remained fairly constant, but obesity and severe obesity rates have increased dramatically. Data collected by the CDC in Figure 7.22 show rising obesity among men and women from about 10 percent in 1960 to more than 40 percent in 2018.  Severe obesity was almost nonexistent in 1960 and is approaching 10 percent of the female population today.

Childhood Obesity

These trends are clear and are not limited to adults. Rates of obesity among children have also increased sharply over the past several decades. This is especially concerning because the health and metabolic effects of excess body weight can accumulate over a lifetime.

As shown in Figure 7.23, fewer than 5% of children were classified as obese in 1960. Today, that number has increased to about 20%. Small declines in the early 2000s may be linked to increased public awareness and prevention efforts. For example, Let’s Move!, launched by Michelle Obama, aimed to promote healthier eating and physical activity among children.^[3] However, many of these initiatives were not sustained over time.

Obesity among Minority Groups

While obesity affects people across the United States, it does not affect all groups equally. More recent data show that obesity prevalence remains higher among non-Hispanic Black (about 49%) and Hispanic adults (about 45%) compared with non-Hispanic White adults (about 42%). Non-Hispanic Asian adults continue to have the lowest prevalence (about 17%).  ^[4] (Recall from Section 7.3 that although Asian populations tend to have a higher percentage of body fat at a given BMI, obesity rates based on BMI classifications are still lower than in other groups.)

Socioeconomic differences also persist. Adults with higher levels of education and income are generally less likely to have obesity. These disparities highlight the importance of considering social and environmental factors when examining causes and solutions. Not everyone has the same opportunities for good health or the same ability to make lifestyle changes, due to poverty and long-standing inequities in access to resources such as safe neighborhoods, healthy foods, and healthcare.

Global Obesity

The obesity epidemic is not unique to the United States; it is a global health challenge. Recent estimates indicate that more than 1 billion people worldwide are living with obesity, including adults, adolescents, and children. ^[5]   Among children and adolescents aged 5 to 19 years, the global prevalence of overweight and obesity has risen dramatically—from about 8% in 1990 to more than 20% in recent years.  ^[6]

In the past, obesity was more common in high-income countries. Today, it is increasing rapidly in low- and middle-income countries as well. This shift is largely linked to changes in food environments, including greater availability of inexpensive, energy-dense, highly processed foods, along with reduced physical activity. ^[7]

Despite the seriousness of the issue, no country has successfully reversed obesity trends at the population level. The World Health Organization set a global target to halt the rise in obesity by 2025, but most countries have not met this goal. ^[8]  Addressing the epidemic will require a better understanding of its complex causes, including biological, behavioral, environmental, and social factors. Meaningful progress will depend on coordinated efforts that address these underlying drivers.

Causes of the Obesity Epidemic

If obesity were an infectious disease spreading rapidly across the globe—affecting billions of people’s health, longevity, and productivity—it likely would have prompted an urgent, coordinated global response similar to the one seen during the COVID-19 pandemic. Governments, researchers, and pharmaceutical companies would mobilize quickly to develop vaccines and treatments to stop its spread.

However, obesity is far more complex than a single infectious agent. It does not have one clear cause or a simple solution. Instead, it results from the interaction of many factors, including biology, behavior, environment, culture, and socioeconomic conditions. Addressing obesity requires more than a medical treatment—it calls for comprehensive, long-term strategies that improve food environments, increase opportunities for physical activity, and reduce health disparities.

Behavior

At its core, rising obesity is caused by a chronic shift towards eating too many calories each day, leading to an often gradual but persistent increase in body weight. People often assume that this is an individual problem. Those who weigh more simply need to change their behavior by eating less and exercising more.  If this doesn’t work, it must be because of a personal failing, such as a lack of self-control or motivation.

While behavior patterns such as diet and exercise can have a significant impact on a person’s risk of developing obesity (as we’ll cover later in this unit), the environments we live in also significantly impact our behavior and make it much harder to maintain energy balance.

Environment

As noted earlier, many of us live in what researchers and public health experts call “obesogenic environments.” That is, how our neighborhoods are built influences our physical activity and food intake, encouraging weight gain.  Human physiology and metabolism evolved in a world where obtaining enough survival food required significant energy investment in hunting or gathering—very different from today’s world, where more people earn their living in sedentary occupations. From household chores to workplace productivity to daily transportation, getting things done requires fewer calories than it did for past generations.

Our jobs have become more and more sedentary, with fewer opportunities for non-exercise thermogenesis (NEAT) throughout the day. There’s less time in the school day for recess and physical activity, and fears about neighborhood safety limit kids’ ability to get out and play after school. Our towns and cities are built more for cars than for walking or biking. We can’t turn back the clock on human progress, and finding a way to stay healthy in obesogenic environments is a significant challenge.

Our environments can also impact our food choices. We’re surrounded by vending machines, fast-food restaurants, coffee shops, and convenience stores that offer quick, inexpensive access to calories. These foods are also heavily advertised, and especially when people are stretched thin by working long hours or multiple jobs, they can be a welcome convenience. However, they tend to be calorie-dense (and less nutrient-dense) and more heavily processed, with levels of sugar, fat, and salt optimized to make us want to eat more than in home-cooked food. In addition, portions, especially in fast-food chain restaurants, have increased over the decades, and people are eating out more and cooking at home less.

Poverty and Food Insecurity

Living in poverty usually means living in a more obesogenic environment. Consider the fact that some of the poorest neighborhoods in the United States—with some of the highest rates of obesity—are often not safe or pleasant places to walk, play, or exercise. They may have heavy traffic and polluted air. They may lack sidewalks, green spaces, and playgrounds. A person living in this type of neighborhood will find it much more challenging to get adequate physical activity compared with someone living in a neighborhood where it’s safe to walk to school or work, play at a park, ride a bike, or go for a run.

In addition, poor neighborhoods often lack grocery stores where people can purchase fresh fruits and vegetables and basic cooking ingredients. Such areas are called “food deserts”—where healthy foods simply aren’t available or easily accessible.

Another important concept in discussing obesity risk is food insecurity. Food security is defined as access by all people at all times to enough safe and nutritious food to support an active, healthy life.  ^[9] In contrast, food insecurity refers to a lack of consistent access to enough food.

Although it may seem counterintuitive, food insecurity in the United States is associated with a higher risk of obesity, as well as chronic conditions such as type 2 diabetes and hypertension. This relationship is influenced by the cost and availability of food. Lower-cost foods are often energy-dense and nutrient-poor, meaning they are high in calories but low in essential nutrients. When these foods make up a large portion of the diet, they can contribute to both excess weight gain and nutrient deficiencies.

Recent data indicate that about 12–13% of U.S. households experience food insecurity.² Disparities persist, with higher rates observed among non-Hispanic Black (approximately 22%) and Hispanic (about 20%) households compared to the national average.^[10] These patterns highlight the role of social and economic factors in shaping both food access and health outcomes.

Genetics And Weight Status

What about genetics? It is well established that genes influence a person’s susceptibility to obesity, but they do not explain the rapid rise in obesity rates over recent decades. In the United States, adult obesity prevalence has increased from about 15% in the late 1970s to over 42% today.  ^[11]  Because genetic changes occur over many generations, this dramatic increase—occurring within just a few decades—cannot be explained by genetics alone.

Instead, the rise in obesity is largely driven by environmental factors, including increased availability of energy-dense foods, larger portion sizes, and more sedentary lifestyles. When our grandparents were children, they were much less likely to develop obesity—not because their genes were different, but because they lived in a different food and activity environment.

That said, genetics still plays an important role at the individual level. Research suggests that 40% to 70% of the variation in body weight may be influenced by genetic factors.  ^[12]  Certain genes can affect appetite regulation, satiety, fat storage, and energy expenditure. For example, some individuals may feel hungrier, experience reduced fullness, or burn fewer calories at rest. These genetic differences help explain why obesity tends to run in families and why some people are more vulnerable in today’s “obesogenic” environment.

Solutions to the Obesity Epidemic

Because obesity has many causes, addressing it requires multiple strategies at the individual, community, and policy levels. Since obesity often develops over time and can be difficult to reverse, many efforts focus on prevention—beginning early in life. In this section, we highlight approaches used in schools, communities, and at the state and federal levels.

Support Healthy Dietary Patterns

Interventions that promote healthy dietary patterns—especially among individuals and communities affected by food insecurity or poverty—can help reduce obesity risk. Evidence shows that some strategies are effective, while others are still being evaluated for long-term impact.

Examples include:

• Improve nutrition standards in key settings.
  Strengthening nutrition standards in childcare, schools, hospitals, and worksites can improve diet quality across populations. Programs supported by the US Department of Agriculture have been linked to healthier food choices among children. ^[13]
• Limit marketing of less healthy foods.
  Reducing advertising of highly processed, energy-dense foods—especially to children—is recommended by the World Health Organization to help prevent obesity.  ^[14]
• Increase access to healthy foods.
  Incentives for supermarkets and farmers’ markets in underserved areas can improve access to fresh, nutrient-dense foods and reduce reliance on convenience foods.
• Provide clear nutrition information.
  Menu labeling and nutrition education can increase awareness and support informed decision-making.
• Improve food assistance programs.
  Enhancing the nutritional quality of foods available through assistance programs can help reduce disparities in diet-related health outcomes.
• Use economic strategies.
  Policies such as taxes on sugar-sweetened beverages may reduce consumption of added sugars.
  

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Calories on Menu Labels

Beginning in 2018, as part of the Affordable Care Act, chain restaurants with 20 or more locations were required to display calorie information on menus.

Research on the effectiveness of menu labeling is mixed. Some studies show that calorie information leads to lower-calorie choices, particularly among health-conscious consumers, while others show little effect.  ^[15] Food choices are influenced by many factors, including cost, taste preferences, and access to food. For individuals experiencing food insecurity, higher-calorie options may provide more perceived value for the price.

Newer strategies may enhance the impact of menu labeling. For example:

• Interpretive labels (such as “traffic light” symbols) can make nutrition information easier to understand.
• Menu design matters—placing calorie information on the left side of menus (where people read first) has been shown to influence choices more than placing it on the right.  ^[16]

There is also evidence that menu labeling may encourage restaurants to offer lower-calorie and more nutrient-dense options. ^[17]

Healthy Food Assistance Programs

In 2009, the US Department of Agriculture updated the food packages for the WIC Program to better align with the Dietary Guidelines for Americans. The revised packages increased fruits, vegetables, whole grains, and low-fat dairy while reducing juice. Following these changes, improvements in diet quality and modest declines in childhood obesity among participants were observed. ^[18]

The Supplemental Nutrition Assistance Program (SNAP) does not restrict the types of foods that can be purchased, but many farmers’ markets now accept SNAP benefits, improving access to fresh produce. ^[19]

Sugar-Sweetened Beverage Taxes

Sugar-sweetened beverages—such as soda, fruit drinks, and sports drinks—are major sources of added sugars and contribute to excess calorie intake.

Local taxes on these beverages have been implemented in several U.S. cities. Although controversial, early evidence suggests that these taxes reduce purchases and consumption of sugary drinks.  ^[20]

Other countries have taken different approaches. For example, the United Kingdom implemented a tax on beverage manufacturers based on sugar content. This policy led to product reformulation, resulting in a substantial reduction in the average sugar content of soft drinks. ^[21]

Given the multiple causes of obesity, solving this problem will also require many solutions at different levels. Because obesity affects people over the lifespan and is difficult to reverse, many of these efforts focus on prevention, starting as early as the first year of life. We’ll discuss individual weight management strategies later in this chapter. Here, we’ll review some strategies happening in schools, communities, and at the state and federal levels.

Calories on Menu Labels

Beginning in 2018, as part of the Affordable Care Act, chain restaurants with more than 20 locations were required to add calorie information to their menus. There isn’t enough research to say whether having this information improves customers’ choices; some studies show an effect, and others don’t.¹⁰ Many factors influence people’s decisions, and the type of restaurant, customer needs, and menu presentation all likely matter. For example, some studies show that health-conscious consumers choose lower-calorie menu items when presented with nutrition information.  Still, people with food insecurity may understandably choose higher-calorie items to get more “bang for their buck”.¹¹

Research has also shown that adding interpretative images—like a stoplight image labeling menu choices as green or red as shorthand for high or low nutrient density—can help. And a 2018 study found that when calorie counts are on the left side of English-language menus, people order lower-calorie menu items. Putting calorie counts on the right side of the menu (as is more common) doesn’t have this effect, likely because the English language is read from left to right.¹² Some studies have also found that restaurants that implement menu labeling offer lower-calorie and more nutrient-dense options, indicating that menu labeling may push restaurants to look more closely at the food they serve.^10,13

WIC Foods

In 2009, the USDA revised the food packages for the Women, Infants, and Children (WIC) program to align with the Dietary Guidelines for Americans. The new packages emphasize more fruits, vegetables, whole grains, and low-fat dairy, and decrease the availability of juice. After this change, the obesity rates of children in the WIC program decreased.  The Supplemental Nutrition Assistance Program (SNAP) currently has no guidelines for the nutrient content of foods recipients can purchase.  Therefore, SNAP funds can be used to purchase any food. Fortunately, many farmers’ markets now accept SNAP benefits for the purchase of fresh fruit and vegetables.³ 

Sugar Taxes

Soda, fruit punch, and sports drinks are loaded with added sugar.  This sugar contributes significant empty calories to the U.S. diet and is associated with childhood obesity. Local taxes on soda and other sugary drinks are often controversial, and soda companies lobby to prevent them from passing. However, early research in U.S. cities with soda taxes shows that they do reduce soda consumption.³ The United Kingdom has taken a different approach. They started taxing soft drink manufacturers for the sugar content of the products they sell. Between 2015 and 2018, the average sugar content of soda sold in the U.K. dropped by 29 percent.¹⁴

Support Physical Activity

Increasing physical activity increases the energy expended during the day. This can help maintain energy balance, thus preventing weight gain. It may also help to shift a person into a negative energy balance and facilitate weight loss if needed. But simply adding an exercise session—a run or a trip to the gym, say—often doesn’t shift energy balance (though it’s undoubtedly good for health). Why? Exercise can increase hunger, and there are only so many calories a person can burn in 30 or 60 minutes. That’s why it’s also important to look for opportunities for non-exercise activity thermogenesis (NEAT); that is, find ways to increase movement throughout the day.  

• Schools should have physical education classes and recess. In addition to helping kids stay healthy, movement also helps them learn.

• Make neighborhoods safer and more accessible for walking, cycling, and playing.
• When safe, encourage kids to walk or bike to school.
• Build family and community activities around physical activity, such as trips to the park, walks together, and community walking and exercise groups.
• Facilitate more movement in the workday by encouraging walking meetings, movement breaks, and treadmill desks.
• Find ways to move that are enjoyable to you and fit your life. Yard work, walking your dog, playing tag with your kids, and going out dancing all count!
  

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Attributions

This section is an adaptation of “Obesity Epidemic: Causes and Solutions” in Nutrition: Science and Everyday Application, v. 1.0 by Alice Callahan, PhD; Heather Leonard, MEd, RDN; and Tamberly Powell, MS, RDN, licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.