One of the best parts of my job as a pediatrician is meeting my patients as infants and watching them grow into teens. In doing this, I take my responsibility of counseling kids and parents on healthy ways to live seriously.
When your children come in for their annual well visits, we check their physical and mental health. One way we measure physical well-being is through understanding their body mass index (BMI). What exactly is BMI and why is it important to your child’s health now and as they grow into adulthood?
The easiest way to explain BMI is a calculated measurement of someone’s weight in relation to their height. The first part of your child’s annual well visit includes a stop to get your child’s height and weight without shoes or heavy clothing like a jacket. With a calculation of these numbers, we can get a quick estimate of a child’s weight in relation to their height. This number on their growth chart lets us know if your child is underweight, normal weight, overweight or in some cases obese.
Every child grows differently, so as pediatricians we take this into account. More acutely, boys and girls have differences in body fat distribution with a range of normal body shapes and sizes. BMI percentiles factor in a child’s growth and age to determine if they are within a healthy weight range.
BMI doesn’t tell the whole story. It’s not a perfect measurement, but it does guide us. Shorter kids with an athletic build can have a higher BMI. Some kids can be within a healthy range for BMI but do not eat healthy and get little activity. Conversely, there are some kids who are active and eat healthy, and still have a high BMI. We take all of this into account when meeting with our patients and counsel them accordingly.
One thing that has come up is the question of BMI and race. In 2009, a study of 1,300 young adults by the British Journal of Nutrition concluded BMI may over and under represent obesity in certain races. Since the BMI scale was largely derived from data using older white adults, it does not take into account the varying body fat percentage, muscle density or bone size of different ethnic groups. While that may be true for adults, it is not the case for children.
While adult BMI uses value ranges (less than 18.5 is considered underweight, over 30 is considered obese, etc…), for children we use percentiles, which allow for more flexibility and take into account a child’s growing body. Furthermore, these percentiles were developed using multiple surveys of thousands of children in the United States between 1963 and 1994, so they’re far more representative and inclusive.
While being aware of implicit bias is always important in health care, it’s also important to remember that BMI is not a diagnostic tool and is only one piece doctors consider — along with diet, physique, physical activity and family medical history — when assessing a child’s overall health and well-being.
I like to see when kids’ BMI falls between the 5th and 85th percentile. Kids above or below could have nutritional shortfalls, either not eating enough or eating too much. Low BMI can also be affected by needing more nourishing food to fuel activities, while a high BMI can indicate a need for increased activity and to incorporate healthier eating habits. Less commonly, medical conditions, illnesses and medications are just a few instances that can affect a person’s ability to maintain a healthy weight.
Children with a BMI above the 85th percentile are at risk for problems as they get older such as diabetes, high blood pressure, chronic joint pain, sleep apnea and psychosocial stress such as bullying and low self-esteem. Research shows that children who fall within the overweight and obese ranges tend to take that extra weight into adulthood. However, it is never too late to make healthy and positive changes for your family, which I talk about a little later in this blog.
It can be hard to keep your BMI in a healthy range. Over the past year, a lot of families have done a good job staying home to reduce the risk of spreading COVID-19, but have increased some other unhealthy habits such as more frequent snacking and increased screen time.
So to keep BMI in a healthy range, I recommend a few strategies for patients and their families.
I offer these tips with caution. Don’t ever put your kids on a fad diet or incorporate an exercise program without talking to your pediatrician first. Children have unique nutritional needs for their healthy growth and development. Involve your kids in choosing healthy snacks and meal preparation if you can. There are a lot of cookbooks and websites dedicated to making healthy, kid-friendly snacks and meals. My go-to website for families is healthychildren.org (the American Academy of Pediatrics website for families). The section on nutrition includes healthy recipes and short articles about a variety of nutrition topics from strategies for tackling picky eating to discussing alternatives to cow’s milk.
Your pediatrician also has many resources for helping patients and families live healthy lives. If you have any concerns about your child’s well-being or want some help incorporating healthier habits into your family’s routine, check with your pediatrician for more resources. It’s what we are here for!