Obesity is generally defined as weighing more than 20 percent above the ideal number of pounds for your height and age. The percentage of teens that are overweight or obese has more than doubled in the last three decades. Approximately 12.5 million or 17 percent of children aged 2 through 19 are considered overweight, according to the National Institute of Child Health and Human Development.

Causes

Teen obesity occurs when too few calories are burned for the number of calories consumed. Genetics or family history as well as behavior and environmental factors can influence whether a young person becomes obese. High-calorie fast foods, beverages, more meals eaten in restaurants, and larger, often super-sized portions all may contribute to teen obesity.

Teen diets often don't meet nutrition guidelines. For example, only 8 percent of children in Colorado ate vegetables three or more times per day as recommended by the U.S. Department of Agriculture, reports Colorado University Extension Service.

Health Effects

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Childhood obesity can have both short- and long-term health consequences 3. Overweight kids are more likely to be overweight in adulthood. In a study published in January 2007 in "Journal of Pediatrics," lead researcher David S. Freedman found that 70 percent of obese children aged 5 to 17 had one or more risk factors for cardiovascular disease. Eight to 45 percent of newly diagnosed cases of Type 2 diabetes are in children and teens, according to the National Institute of Child Health and Human Development or NICHHD.

Ethnic Disparities

Teen obesity rates vary significantly among different races, ethnicities and income levels. For example, in 2008, the CDC noted that Hispanic teen boys were more likely to be obese than non-Hispanic white boys, while non-Hispanic, black teen girls were more apt to be obese than non-Hispanic white girls. Low-income families may not be able to afford healthier food options such as fruits and vegetables and may not have easy access to safe areas for physical activity.

Prevention

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Eating a well-balanced diet that includes lean meat, fruits, vegetables and whole grains combined with regular exercise can help prevent overweight and obesity. Small changes, such as eliminating one can of soda per day and spending less time watching TV can contribute to a healthier lifestyle. Children and teenagers should spend 60 minutes a day engaged in some type of physical exercise.