Risk Factors
Where you live plays a role in your risk for obesity. Simply living in the United States makes a person more susceptible to obesity. The prevalence of obesity in America has risen dramatically over the past few years and continues to increase.
- According to a 2002 analysis of government data, 30.5% of American adults are obese (BMI over 30) -- up from about 23% in the early 1990s.
- The number of those who were overweight also increased during that time -- from about 56% to a current rate of 64.5%.
- At least 2% of the population is severely obese (more than 100 pounds overweight). This rate has quadrupled over the past 25 years.
- Obesity has increased in every state, in both men and women, across all age groups, and in every ethnic group, although some groups may face slightly higher risks than others.
Risk by Age. People of any age are at risk for obesity. More children and adolescents are overweight in America than ever before. Gaining some weight is inevitable with age and adding about 10 pounds to a normal base weight over time is not harmful. The current weight gain in American adults over 50, however, is significant. By age 55, the average American has added nearly 40 pounds of fat during the course of adulthood. This condition is made worse by the fact that muscle and bone mass decrease with age.
Risk by Gender. In men, BMI tends to increase until age 50 and then it levels off. In women, weight tends to increase until age 70 before it plateaus. A 2000 study has found that there are three high-risk periods for weight gain in women.
- The first is at the onset of menstruation, particularly if it is early. (Obesity in childhood may actually be a contributor to early puberty, which in turn increases the risk for more weight gain.)
- The second is after pregnancy, with higher risk for women who are already overweight.
- Finally, many women gain weight after menopause.
These findings are significant because they may allow women to target high-risk times, and consequently prevent unnecessary weight gain.
Risk by Economic Group. Obesity is more prevalent in lower economic groups. One 2002 study reported that women who reported that they did not have enough food were more likely to be overweight than those who said they had sufficient food. Researchers discovered that the low-income women tended to have fewer fruits and vegetables but were actually taking in more calories a day than higher-income women. In any case, obesity it is increasing in young adults with college education along with everyone else.
Ethnic Groups. Among ethnic groups in general, African American women are more overweight than Caucasian women but African American men are less obese than Caucasian men. (Currently, 80% of African American women are overweight.) Hispanic men and women tend to weigh more than Caucasians.
US Regions. Regionally, the prevalence of obesity is lowest in the Western states and highest in the South.
Dietary Habits That Increase Risk
A number of dietary habits put people at risk for becoming overweight:
- Night-Eating Syndrome. Night-eating syndrome is defined as having no appetite in the morning, insomnia, and consuming more than half of daily food intake after 6:00 PM. It is associated with obesity and is difficult to treat. Stress reduction and relaxation techniques may be helpful.
- Binge Eating and Eating Disorders. About 30% of people who are obese are binge eaters who typically consume 5,000 to 15,000 calories in one sitting. To be diagnosed as a binge eater, a person has to binge at least twice a week for 6 months. Many experts believe that binge-eating carbohydrates causes an increase in a natural opiate leading to dependence on carbohydrates, and, therefore, the condition should be treated as an addiction. Other eating disorders are bulimia and anorexia. Bulimia is binge eating followed by purging in order to lose weight. Anorexia nervosa is a mental illness in which the person refuses to maintain weight at the normal level because of a terrible fear of getting fat and an abnormal perception of what his or her body looks like. Both conditions pose risks for serious medical problems, and anorexia nervosa can be life threatening. A combined approach using behavioral therapy and antidepressants may help these individuals. [For more information, see In-Depth Report # 49, Eating disorders.]
- Restrained Eating. Some people, mostly middle-aged women who have normal weight, have a pattern referred to as restrained eating. This pattern requires a high level of conscious control and usually maintains a lower weight. However, such restraint places these individuals at higher risk for loss of control and subsequent overeating.
- Infrequent Eating. There is some evidence to suggest that eating small frequent meals uses more calories than infrequent large meals. It should be strongly noted, however, that packaged snack foods add calories and some do not produce a feeling of being full, so that people simply eat more than they should.
Specific Groups at Risk
Anyone with Sedentary Lifestyles. Office workers, drivers, and anyone whose lifestyle involves sitting for long periods are at higher risk for obesity.
Ex-Smokers. The trend toward weight increase has followed the trend for quitting smoking. Nicotine increases the metabolic rate, and quitting, even without eating more, can cause weight gain, which may be considerable. It is important to note that weight control is not a valid reason to smoke. People in previous centuries did not smoke cigarettes, nor were they usually obese.
Shift-Workers. A recent study found that individuals who work late shifts (between 4 PM and 8 AM) tend to eat more and take longer naps than day workers and are more likely to gain excess weight.
People with Disabilities. Obesity rates are higher than average in people with physical or mental disabilities. Those with disabilities in the lower part of the body, such as the legs, are at highest risk.
Obesity in Children: Special ConsiderationsObesity in children and adolescents is rising at an alarming rate. Currently over 15% of young people over 6 years old are obese, and obesity is also increasing children age 5 and younger. Definition of Obesity in Children Children are considered to be overweight if the BMI is over 85% of the weight group in their age and sex categories. If it is 95% and over, they are considered to be obese. Adolescents are generally judged according to adult criteria for obesity, although there are other considerations in this population. Ethnic variations, timing of growth spurts, and higher normal fat levels around puberty can cause disparities in these measurements. Causes and Risk Factors for Obesity in Children Lifestyle Factors. Without educational or parental guidance, children are extremely vulnerable to the intense cultural pressures that are largely responsible for the obesity epidemic. The following are some specific problems created by the culture:
Neither the media nor the educational system has strong well-financed programs that encourage healthy alternatives, including exercise and healthy foods. Family History. Parental obesity more than doubles the risk that a young child, whether thin or overweight, will become obese as an adult. In older children and teenagers, obesity in parents starts to count less as a predictor for body weight than their own weight. The risk for may be due to environmental or genetic factors, or both. Ethnic and Socioeconomic Factors. As in adult populations, children from lower socioeconomic groups and minority populations are at higher risk for obesity. For example, among young Mexican Americans and African Americans, there has been an increase in overweight prevalence of about 13% to over 23%. Factors Surrounding Birth. The following factors surrounding birth are associated with a child's weight:
Although some small studies have reported protection against obesity from breastfeeding, evidence is weak. In a 2003 study, for example, children who were breast fed for three to five months had a lower risk for obesity, but prolonged breastfeeding had no effect. Nevertheless, given the healthful effects of breast feeding and the possibility that it may have even a slight impact on childhood obesity, it is highly recommended. Biologic Effect of Childhood Obesity on Adult Weight Achieving a healthy weight becomes more difficult as children get older. The odds of obesity persisting into adulthood ranges from 20% in 4 year olds to 80% in teenagers. One reason for the persistence is biological. The fat cells change in number or mass depending on a person's age:
Health Consequences of Childhood Obesity Children and adolescents who are obese have poorer health than other children. Studies are reporting unhealthy cholesterol levels and high blood pressure in obese children and adolescents. Of great concern is the dramatic increase in type 2 diabetes in young people, which is most certainly largely due to the increase in obesity. Obesity in children is also linked to asthma, gallbladder problems, sleep apnea, and liver abnormalities. Childhood obesity may be partly responsible for the declining age for onset of puberty in girls, with subsequent risks for breast cancer. It is not clear yet how many of these childhood problems persist in people who achieve normal weight as adults. Staying overweight into adulthood certainly confers health risks. Managing Overweight and Obese Children Childhood obesity is best treated by a non-drug, multidisciplinary approach including diet, behavior modification, and exercise. Some evidence suggests that reducing calories by only 200 to 260 per day would prevent weight gain in most overweight children. Here some tips for children who are overweight:
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