The causes of childhood obesity are usually related to lifestyle choices, although they may also be caused by biological or genetic factors. Lack of exercise and poor diet are the most common causes of this condition. Childhood obesity can lead to a multitude of other health problems in children, including such conditions as high blood pressure, high cholesterol, and diabetes. According to the World Health Organization, a child or adolescent is considered obese if his or her Body Mass Index (BMI) is greater than 30.
It is generally believed that one of the primary causes of childhood obesity is lack of physical activity. A 2005 Kaiser Family Foundation study found that most children spend an average of 44.5 hours a week either watching television or using a computer or game console. Many children also do not walk to school, and spend the majority of their school day sitting behind a desk. These children continue to consume calories, but do not burn those calories with exercise. Therefore, the excess calories are converted to fat.
Television viewing often goes hand in hand with snacking on empty calories, another of the primary causes of childhood obesity. Studies conducted at the University of North Carolina show that junk food and snacks make up almost a third of the average daily calorie intake of most American children. High calorie snacks and beverages are often available to children from vending machines at school. Since the snacks are convenient and often appealing to children, they frequently fill up on unhealthy fare rather than eating complete nutritional meals.
Another poor diet choice that contributes to childhood obesity is the frequent consumption of fast food. For many children and adolescents, going to a fast food restaurant is the most convenient way of getting a quick and inexpensive lunch. Fast food advertising is often directed at children and teens, and young children are sometimes further enticed by the promise of a toy surprise with a meal. The fare at fast food restaurants is usually caloric, providing fat, protein and carbohydrates but lacking in fresh fruits and vegetables.
Some causes of childhood obesity appear to be linked to the health of the pregnant mother. A mother who smokes while pregnant is more likely to have an obese child, as is a mother who is overweight during her pregnancy. Studies have also shown that babies who are breast-fed are less likely to become obese or overweight.
Genetic causes of childhood obesity are sometimes difficult to diagnose. In some families, poor eating habits and a sedentary lifestyle are passed from parents to their children. However, some children do have a genetic predisposition for overweight. Research suggests that some obese children share a genetic abnormality that may be the cause of their weight gain.