Researchers use the term obesogenic environment to describe surroundings that make it easier to consume excess calories and harder to be physically active. Today, obesity affects more than two in five U.S. adults and about one in five children.^[1] However, many of these initiatives were not sustained over time.

Causes of the Obesity Epidemic

Obesity is a complex condition with no single cause. It develops through the interaction of biological, behavioral, environmental, cultural, and socioeconomic factors. As a result, preventing and treating obesity requires more than simply focusing on individual choices.

Behavior

Weight gain ultimately occurs when calorie intake exceeds calorie expenditure over time. Dietary habits and physical activity patterns therefore play an important role in obesity risk. However, obesity is not simply the result of poor choices or a lack of willpower. The environments in which people live, work, and learn can strongly influence eating and activity behaviors.

Environment

Many people live in what researchers call obesogenic environments—surroundings that make it easier to consume excess calories and harder to be physically active. Compared with previous generations, many jobs require less physical labor, transportation relies more heavily on automobiles, and daily life generally involves less movement.

Food environments have also changed. Fast-food restaurants, convenience stores, vending machines, and other sources of inexpensive, calorie-dense foods are widely available. These foods are often heavily marketed, highly processed, and served in large portions. Together, these factors can make maintaining energy balance more challenging.

Figure 7.24. Some elements of our environment that may contribute to weight gain include sedentary jobs, easy access to inexpensive calories, and communities designed more for automobiles than physical activity.

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

Poverty is often linked to more obesogenic environments. Some low-income neighborhoods may have fewer safe places for physical activity and limited access to grocery stores that sell affordable, nutritious foods. As a result, maintaining a healthy diet and active lifestyle can be more challenging.

Another factor associated with obesity risk is food insecurity, which refers to a lack of consistent access to enough safe and nutritious food to support an active, healthy life.^[2]  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.  ^[3]  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.

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.