Baby BMI

Michelle Reich had no concerns about her firstborn daughter’s weight. Her seven-and-a-half-pound newborn, Hannah, had quickly blossomed into a healthy, precocious toddler with rosy cheeks, sparkling hazel eyes, and dark-blonde curls. True, Hannah was larger than some of her peers, but that seemed like a positive sign, says Reich. “She elicited coos of ‘What a yummy baby with all those rolls!’” she says. “I had no reason to believe her weight was anything but an asset.”

But at Hannah’s two-year checkup, her doctor seemed to disagree. She got right down to business, replaying Hannah’s height and weight stats with a critical pause between the two: 75th percentile for height, but 99th percentile for weight. Not off the charts, but almost. Then, a pointed question: “Is she active?”

“It felt like a thinly veiled accusation,” Reich says. “It was the first time I felt like I had to justify her weight.” Reich left the visit with a chart listing Hannah’s BMI as overweight and a looming worry: Did Hannah’s adorably soft arms and rounded belly signal future weight worries? Should Michelle be watching her calorie intake? It seemed crazy, she recalls. “I kept thinking, she’s two!”

Nobody wants to be hassled about their child’s weight. And judging sweetly squishy thighs and chubby cheeks by a grown-up metric like BMI (or body mass index, a measure of weight divided by height squared) just seems wrong. Some say it is. Because BMI is a two-dimensional measurement of body mass that doesn’t take into account the fact that humans are three-dimensional, or account for differences in age and build, critics say the equation doesn’t add up, and that BMI needs to be reworked in order to have validity as a health measurement.

And even if BMI is a valid tool, having one on the higher side isn’t necessarily bad; doctors see plenty of patients with a high BMI and otherwise stellar health, and the BMI of athletes with fit, strong bodies can label them as obese. But Hannah’s doctor’s concern wasn’t completely unfounded. Over the last decade, a number of studies have shown a link between BMI in early childhood and obesity later in life. A new study shows that a child’s BMI at age one and age five might be predictive of future weight. 

Bodies are beautiful in any shape and size and having one that’s particularly big or small isn’t problematic; obesity, however, is linked to an increased likelihood of having diabetes, sleep apnea, high blood pressure, and stroke—health problems parents would just as soon help their kids avoid if possible. With U.S. obesity reaching epidemic levels, some pediatricians are taking note of babyhood body mass and asking parents to watch their children’s activity levels. However, some doctors are more focused on the child’s overall health.

“When I am assessing a baby’s health, I am looking at their growth over time, typically on a growth chart. The growth chart consists of weight, length, and head circumference for infants from zero to two years old and weight and height for toddlers two to four years. The BMI chart begins at three years old. The growth chart plots a child or infant on a scale compared to other children or infants of the same age and gender,” says Dr. Margaret Patterson, pediatrician with Our Lady of the Lake Children’s Health. “My assessment of their growth is not which percentile they are but whether they maintain a consistent growth pattern.”

What types of food the baby is consuming is also a factor in measuring healthy weight. “In infancy, most babies are eating and drinking the same things such as breastmilk and baby food and therefore, I focus more on making sure babies are gaining enough weight not whether they weigh too much. Once introduction of table foods occurs around 9 months and really, after 12 months do I start to get more concerned about the influence of food choices in overall health. Overall health is more important than just one measurement in the office and the trend over time is the best way to look at health,” Dr. Patterson explains. 

With the BMI chart beginning at three years old, the chart isn’t the most reliable way to measure a child’s overall health for little ones. “BMI is not used until three years of age and therefore in babies is not a useful tool. Growth charts over a period of time are helpful but not a single specific point in time. Using BMI after age three can be a good guide but not the sole thing to rely on when assessing health. Pediatricians would like children's BMIs to lie between the 5-95 percent range. When the BMI is above the 95 percent range, I focus on making sure food choices remain low sugar and low fat. With introduction of table foods for babies, I discourage juices and junk foods. If parents can make healthy food choices from the beginning for their children, then they are less likely to have to backtrack and make changes later,” says Dr. Patterson.

And, according to the study, it’s not necessarily body weight itself but a steep weight increase in the first year of life that could point to future weight struggles.

When, like Reich, you have a kid with a healthy lifestyle—high on physical activity, low on junk food—and a higher BMI, don’t stress too much. Dr. Patterson shares, “Parents should assess their child’s health when their child’s BMI is above the 95 percent. If their child is below the 5 percent in BMI, then they should also have a discussion with their child’s pediatrician. Similarly, if there is a rapid decline or growth on the baby’s growth chart, then that would alert the parent and pediatrician to discuss the baby’s daily intake.”

Although BMI can be helpful, it is not the ultimate standard for assessing a healthy child. “A healthy lifestyle that includes healthy foods, are important,” says Dr. Patterson. “Keeping active, getting good sleep and avoiding excessive screen time are all important parts to having a healthy lifestyle for children.”

These days, Hannah is a bubbly, active six-year-old with a one-year-old baby sister, who’s also a thriving, happy girl at the top of the pediatrician’s weight charts. Reich takes weight-related guidance with a grain of salt. “We focus on exercise for pleasure, no soda, little processed food. I know my girls are growing the way they were genetically designed to.” ■

Newsletter Signup

Your Weekly guide to Baton Rouge family fun. BR Parents has a newsletter for every parent. Sign Up