I asked many doctors over the years to help me with Juliana’s weight. What was going on? What do I do? I got no help. Her family practice doctor, whom I loved, told me frankly that doctors had no idea what was causing the obesity epidemic among children. She asked Juliana what her favorite vegetable was. Juliana replied “broccoli.” That was the extent of our nutritional counseling. All of the doctors I consulted prescribed “watchful waiting,” what I now think of as the hope that she would “grow into her weight.”
Why does the “grow into their weight idea” persist in the face of the evidence that most overweight children will become overweight adults? In part because it’s almost impossible to lose weight and keep it off on the Standard American Diet if you are sensitive to carbohydrates (and all of us become more sensitive over time if we continue to eat carbohydrates–this is one of the reasons people tend to gain weight as they age). Your doctor knows how little success he or she has counseling patients to lose weight–almost none of them do. The myth allows everyone to postpone the day of reckoning for overweight or obese children.
A friend of mine provided a perfect example of this phenomenon recently. She took her 14 year old to the doctor for a yearly physical, and wanted the doctor to help her discuss weight management with the teen. The teen had recently gained a lot of weight without growing taller, and was clearly becoming uncomfortable with her appearance. But the doctor didn’t. Instead, she said that since the teen was “only” in the 80th percentile for Body Mass Index, she wasn’t overweight, and not to worry about it. The doctor didn’t advise doing anything, even though the teen had gone from the 42nd percentile BMI at her last checkup a year prior to 80th percentile at this checkup. I bet the doctor was relieved that the teen hadn’t crossed the 85 percent threshold, where she would technically be considered overweight, because the doctor knows she doesn’t have any effective information to offer on how the teen can slim down.
The 1977 BMI charts developed by the National Center for Health Statistics were revised, using new empirical data from five national health examination surveys, by the Center for Disease Control in 2000.
In comparing the 2000 to the 1977 charts, the CDC notes:
“For matching statures within the range shown, weights in the 2000 charts tend to be higher than weights in the 1977 charts, especially at larger statures and for girls.” This may or may not be the result of the underlying population becoming heavier, since the data sets and statistical procedures used to develop the two sets of charts were not the same. Jump to report.
While the stature for age charts match very closely, the weight for stature charts diverge. The biggest difference is for girls–the 95th percentile of weight for stature in 1977 is almost the same at heights above 110 cm as the 90th percentile of weight for stature in 2000 (Figure 104). Almost every percentile curve has moved out for girls (except the 5th percentile). The difference is less pronounced for boys, with the lower percentiles tracking closely, and only the 90th and 95th percentiles moving out in the 2000 tables (Figure 103).
So a girl that was “obese,” above the 95th percentile in 1977, would now be classified as only “overweight.” If the underlying population is becoming heavier, then heavier weights will fall in the range of “normal.”
Body Mass Index (BMI) is a ratio of weight to height. It is a screening tool for spotting people who are more likely to develop various health problems from over or underweight, and for tracking that development in children is progressing appropriately. In adults, a BMI Between 18.5 and 25 is considered healthy. Below 18.5 is underweight. Higher than 25 is overweight; higher than 30 is obese.
In children, the BMI is expressed not only as a number, but as a percentile rank. The child or teen is plotted against other kids of the same age. A child who has a BMI greater than 85 percent of children her age is considered overweight; greater than 95 percent is considered obese. A BMI of less than 5 percent is considered underweight.
There is a very wide range of weights that are considered healthy for a given height in children and adults. Juliana’s healthy weight range is between 93 and 136 pounds. My healthy weight range is between 121 and 171 pounds.
Healthy doesn’t mean ideal for the individual. Although a BMI of 24 is considered healthy, most adults will feel better at a much lower BMI. The same is true for children–although a BMI in the 84th percentile will not technically indicate a child is overweight, that child will likely feel better at a lower BMI.