Childhood Obesity, BMI, and a Healthy Tidbit
Adult and childhood obesity has been a major health concern for decades and continues to be so in 2016. Overall obesity rates in children have remained stable for the past several years, but are still very high. Approximately 17% of children ages 2-19 years are obese. This represents 12.7 million children nationwide and many millions more are overweight but not obese. Obesity is defined as having a BMI (Body Mass Index) of greater than 95th percentile. Overweight is defined as having a BMI of greater than 85th percentile but less than 95th percentile.
Body Mass Index is calculated by dividing one’s weight in kg by one’s height in meters squared. The formula for calculating BMI is: BMI = weight (in kg)/height2 (in meters). The actual BMI number is not a particularly useful concept in children because they are constantly growing and at certain times in their growth cycle, the height velocity and weight velocity are at different rates. A BMI of 24 in an adult might be a good BMI, but in an 8 year-old child would represent obesity. A more appropriate concept for children is BMI percentile, which compares the BMI in a child of a given age and gender with the BMI of the rest of the population of children of the same age and gender. Thus, a BMI of greater than 95th percentile represents a child whose BMI is greater than 95 percent of children of the same age and sex, and indicates obesity.
The causes of obesity are very complex and multifactorial, and include race, ethnicity, genetics, behavior, education, socioeconomic status, and outside influences such as food availability and advertising by the food industry.
Two of the most important known behavioral risk factors for childhood obesity are: 1) The consumption of high calorie, sugar sweetened drinks such as fruit juices, soda pop, and sports drinks, and 2) the decline in physical activity and outdoor play brought about by an increase in “screen time” which includes television, computers, phones, tablets, and video games. Elimination of sugar sweetened drinks from children’s diets, and limiting screen time to no more than two hours per day (and thus encouraging physical activity) have been shown to help prevent obesity in children as well as provide benefit in treating children who are already overweight or obese.
A very useful and informative website regarding obesity in both children and adults can be found by searching CDC Division of Nutrition, Physical activity, and Obesity, or go to www.cdc.gov/nccdphp/dnpao/index.html