Obesity is a complex health issue to address. Obesity results from a combination of causes and contributing factors, including individual factors such as behavior and genetics. Behaviors can include dietary patterns, physical activity, inactivity, medication use, and other exposures. Additional contributing factors in our society include the food and physical activity environment, education and skills, and food marketing and promotion.
Obesity is a serious concern because it is associated with poorer mental health outcomes, reduced quality of life, and the leading causes of death in the U.S. and worldwide, including diabetes, heart disease, stroke, and some types of cancer.
Healthy behaviors include a healthy diet pattern and regular physical activity. Energy balance of the number of calories consumed from foods and beverages with the number of calories the body uses for activity plays a role in preventing excess weight gain.1,2 A healthy diet pattern follows the Dietary Guidelines for Americans which emphasizes eating whole grains, fruits, vegetables, lean protein, low-fat and fat-free dairy products and drinking water. The Physical Activity Guidelines for Americans recommends adults do at least 150 minutes of moderate intensity activity or 75 minutes of vigorous intensity activity, or a combination of both, along with 2 days of strength training per week.
Having a healthy diet pattern and regular physical activity is also important for long term health benefits and prevention of chronic diseases such as Type 2 diabetes and heart disease.
For more, see Healthy Weight – Finding a Balance.
People and families may make decisions based on their environment or community. For example, a person may choose not to walk or bike to the store or to work because of a lack of sidewalks or safe bike trails. Community, home, child care, school, health care, and workplace settings can all influence people’s daily behaviors. 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 community environmental factors that have contributed to the obesity epidemic, as well as several community initiatives taking place to prevent and reduce obesity.
Learn about strategies for a Healthy Food Environment and strategies to improve the environment to make it easier to be physically active.
Strategies to create a healthy environment are listed on the Strategies to Prevent Obesity page. More specifically, strategies to create a healthy school environment are listed on the CDC Adolescent and School Health website.
Do Genes Have a Role in Obesity?
Genetic changes in human populations occur too slowly to be responsible for the obesity epidemic. Nevertheless, the variation in how people respond to the environment that promotes physical inactivity and intake of high-calorie foods suggests that genes do play a role in the development of obesity.
How Could Genes Influence Obesity?
Genes give the body instructions for responding to changes in its environment. Studies have identified variants in several genes that may contribute to obesity by increasing hunger and food intake.
Rarely, a clear pattern of inherited obesity within a family is caused by a specific variant of a single gene (monogenic obesity). Most obesity, however, probably results from complex interactions among multiple genes and environmental factors that remain poorly understood (multifactorial obesity).3,4
What about Family History?
Health care practitioners routinely collect family health history to help identify people at high risk of obesity-related diseases such as diabetes, cardiovascular diseases, and some forms of cancer. Family health history reflects the effects of shared genetics and environment among close relatives. Families can’t change their genes but they can change the family environment to encourage healthy eating habits and physical activity. Those changes can improve the health of family members—and improve the family health history of the next generation.3,4
Learn more about genetics and obesity here: 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. The science continues to emerge on the role of other factors in energy balance and weight gain such as chemical exposures and the role of the microbiome.
A health care provider can help you learn more about your health habits and history in order to tell you whether behaviors, illnesses, medications, and/or psychological factors are contributing to weight gain or making weight loss hard.
Consequences of Obesity
People who have obesity, compared to those with a normal or healthy weight, are at increased risk for many serious diseases and health conditions, including the following:5,6,7
- All-causes of death (mortality)
- High blood pressure (Hypertension)
- High LDL cholesterol, low HDL cholesterol, or high levels of triglycerides (Dyslipidemia)
- Type 2 diabetes
- Coronary heart disease
- Gallbladder disease
- Osteoarthritis (a breakdown of cartilage and bone within a joint)
- Sleep apnea and breathing problems
- Some cancers (endometrial, breast, colon, kidney, gallbladder, and liver)
- Low quality of life
- Mental illness such as clinical depression, anxiety, and other mental disorders8,9
- Body pain and difficulty with physical functioning10
For more information about these and other health problems associated with obesity, visit Health Effects of 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 [PDF 56KB].
Economic and Societal Consequences
Obesity and its associated health problems have a significant economic impact on the U.S. health care system.11 Medical costs associated with overweight and obesity may involve direct and indirect costs.12,13 Direct medical costs may include preventive, diagnostic, and treatment services related to obesity. Indirect costs relate to morbidity and mortality costs including productivity. Productivity measures include ‘absenteeism’ (costs due to employees being absent from work for obesity-related health reasons) and ‘presenteeism’ (decreased productivity of employees while at work) as well as premature mortality and disability. 14
National Estimated Costs of Obesity
The medical care costs of obesity in the United States are high. In 2008 dollars, these costs were estimated to be $147 billion.15
The annual nationwide productive costs of obesity obesity-related absenteeism range between $3.38 billion ($79 per obese individual) and $6.38 billion ($132 per obese individual)16.
In addition to these costs, data shows implications of obesity on recruitment by the armed forces. An assessment was performed of the percentage of the US military-age population that exceeds the US Army’s current active duty enlistment standards for weight-for-height and percent body fat, using data from the National Health and Nutrition Examination Surveys. In 2007-2008, 5.7 million men and 16.5 million women who were eligible for military service exceeded the Army’s enlistment standards for weight and body fat.17
The number of people with obesity in the UK has more than trebled in the last 25 years. Doctors now say that the condition is reaching 'epidemic' proportions. Why are they so concerned?
A person is considered obese if they are very overweight with a high degree of body fat.
Some experts believe obesity is responsible for more ill health than smoking. Being significantly overweight is linked to a wide range of health problems, including:
The impact of obesity in the UK
- A Government report recently claimed that obesity will cost the NHS £6.4bn per year by 2015
- In England data from 2011 shows that 24.8% of adults (16 or over) and 16.3% of children (2 -15) are obese
- In Scotland data from 2010 shows 27.4% of adults and 14% of children are obese
- Obesity is most prevalent in the North East of England and in the West Midlands
The most common way to assess if a person is obese is to check their body mass index. BMI is calculated by dividing your weight in kilograms by your height in metres squared.
If your BMI is above 25 you are overweight. A BMI of 30-40 is considered obese, while above 40 is very obese. A BMI of less than 18.5 is underweight.
Another useful method is to take a waist measurement because fat in the centre of the body (apple-shaped obesity) is much more strongly linked to health risks than fat more widely distributed on the arms and legs. Women with a waist of 80cm or greater and men with a waist of 94cm or greater are more likely to develop obesity-related health problems.
A new way of calculating BMI has recently been proposed as the standard assessment is less accurate for extremes of height - the short and the tall. The new calculator hopes to correct this.
On average a physically active man needs around 2,500 calories per day, while a woman needs 2,000. If we eat any more, the extra energy is stored for later use, mostly as fat.
This mechanism was life-saving during our hunter-gatherer days when food was often scarce. However, the boom in plentiful, cheap food, coupled with a general decrease in physical activity, means that those stores of fat are rarely called on. Instead they continue to grow.
So why don't people just stop eating foods high in fat and sugar if they know they can cause physical problems? Scientists are still searching for the answers, but it appears that our brains have been wired to encourage the consumption of calorie-rich foods, even at the expense of good health. Quite simply, these foods bring us pleasure.
One recent study revealed that an area of the brain related to addiction and reward - the nucleus accumbens - lights up when a participant is shown calorie rich, fatty foods compared to healthy food.
Another area of the brain associated with pleasant tastes and reward, called the orbitofrontal cortex, is activated when we eat fatty foods.
Obesity experts say parents are struggling with a multitude of problems when it comes to their child's weight.
They range from a lack of education about food, limited cooking skills, limited money to buy healthy food, long working hours, easy access to snack food and pester power.
Why do parents let their children get fat?
At the same time, people are increasingly living more sedentary lifestyles and therefore burning fewer calories.
Studies have also shown that housewives in the 1950s were significantly slimmer than women today. This could be because their daily lives involved much more physical activity, including walking more and having fewer labour-saving devices.
Therefore, some scientists argue that the rise in obesity is a result of our bodies' inability to adapt to the changing environment.
According to the NHS, another reason obesity is on the rise is because unhealthy eating habits are often passed down through families, due to a lack of good food education.
Unless obesity is tackled, the government predicts that 60% of men, 50% of women and 25% of children in Britain will be obese by 2050.
Obesity expert Dr Tony Goldstone explains why fat is bad for your health, and how even small amounts of exercise can be good for you
For more information on symptoms and treatments, please visit NHS Choices
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