Causes and Consequences

What causes overweight and obesity?

There are a variety of factors that play a role in obesity. This makes it a complex health issue to address. Behavior, environment, and genetic factors may have an effect in causing people to be overweight and obese.

For more, see Healthy Weight – Balancing Calories.

Environment

People may make decisions based on their environment or community. For example, a person may choose not to walk to the store or to work because of a lack of sidewalks. Community, home, child care, school, health care, and workplace settings can all influence people's health decisions. Therefore, it is important to create environments in these locations that make it easier to engage in physical activity and eat a healthy diet.

Watch The Obesity Epidemic to learn about the many environmental factors that have contributed to the obesity epidemic, as well as several community initiatives taking place to prevent and reduce obesity.

Genetics

How do genes affect obesity?

Science shows that genetics plays a role in obesity. Genes can directly cause obesity in disorders such as Bardet-Biedl syndrome and Prader-Willi syndrome.

However genes do not always predict future health. Genes and behavior may both be needed for a person to be overweight. In some cases multiple genes may increase one's susceptibility for obesity and require outside factors; such as abundant food supply or little physical activity.

For more information on the genetics and obesity visit Obesity and Genomics.

Other Factors

Diseases and Drugs
Some illnesses may lead to obesity or weight gain. These may include Cushing's disease, and polycystic ovary syndrome. Drugs such as steroids and some antidepressants may also cause weight gain.

A doctor is the best source to tell you whether illnesses, medications, or psychological factors are contributing to weight gain or making weight loss hard.

What are the consequences of overweight and obesity?

Health Consequences

Research has shown that as weight increases to reach the levels referred to as "overweight" and "obesity,"* the risks for the following conditions also increases:¹

• Coronary heart disease
• Type 2 diabetes
• Cancers (endometrial, breast, and colon)
• Hypertension (high blood pressure)
• Dyslipidemia (for example, high total cholesterol or high levels of triglycerides)
• Stroke
• Liver and Gallbladder disease
• Sleep apnea and respiratory problems
• Osteoarthritis (a degeneration of cartilage and its underlying bone within a joint)
• Gynecological problems (abnormal menses, infertility)

*Overweight is defined as a body mass index (BMI) of 25 or higher; obesity is defined as a BMI of 30 or higher. For more, see Defining Obesity.

For more information about these and other health problems associated with overweight and obesity, visit Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.

Economic Consequences

Overweight and obesity and their associated health problems have a significant economic impact on the U.S. health care system.² Medical costs associated with overweight and obesity may involve direct and indirect costs.^3,4 Direct medical costs may include preventive, diagnostic, and treatment services related to obesity. Indirect costs relate to morbidity and mortality costs. Morbidity costs are defined as the value of income lost from decreased productivity, restricted activity, absenteeism, and bed days. Mortality costs are the value of future income lost by premature death.

National Estimated Cost of Obesity
The medical care costs of obesity in the United States are staggering. In 2008 dollars, these costs totaled about $147 billion.⁵

References

1. NIH, NHLBI Obesity Education Initiative. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Available online: http://www.nhlbi.nih.gov/guidelines/obesity/ob_gdlns.pdf [PDF-1.25Mb]
2. U.S. Department of Health and Human Services. The Surgeon General's call to action to prevent and decrease overweight and obesity. [Rockville, MD]: U.S. Department of Health and Human Services, Public Health Service, Office of the Surgeon General; [2001]. Available from: US GPO, Washington.
3. Wolf AM, Colditz GA. Current estimates of the economic cost of obesity in the United States. Obesity Research.1998;6(2):97–106.
4. Wolf, A. What is the economic case for treating obesity? Obesity Research. 1998;6(suppl)2S𔃅S
5. Finkelstein, EA, Trogdon, JG, Cohen, JW, and Dietz, W. Annual medical spending attributable to obesity: Payer- and service-specific estimates. Health Affairs 2009; 28(5): w822-w831.

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