It's hard to tell whether a child is a healthy weight just by looking. Parents, and even some doctors, may think a healthy-weight child is underweight. Or they may tend to underestimate weight gain in children, says Chris Tiongson, MD, pediatrician at Sanford Children's Health in Fargo, N.D. "Sometimes our eyes fool us," says Tiongson. "It might be because family members or friends are heavier, too."
Toddler's Weight and BMI
This is why growth charts come in handy, Tiongson says. Pediatricians use them and something called body mass index (BMI) to determine if your child may be overweight.
You can start calculating body mass index (BMI) as early as age 2. Kids' BMIs are based on height and weight, like adult BMIs. But then that number is taken and placed on a growth chart to account for your child's age and gender because, unlike adults, kids are still growing. The ending result is not a plain BMI number but rather a BMI percentile. That percentile is also called "BMI for age."
BMI percentiles show where your child's weight falls compared to other kids of the same age and gender. For instance, if your toddler's BMI is in the 75th percentile, she is heavier than 75% of toddlers her age. But at the 75th percentile, she is still in the healthy weight zone.
Here’s how kids' BMI percentiles break down:
- Underweight: less than the 5th percentile
- Healthy Weight: 5th percentile up to the 85th percentile
- Overweight: 85th percentile up to the 95th percentile
- Obese: 95th percentile or greater
Doctors pay attention to potential weight issues if the BMI is below the 5th percentile. A child with BMI percentile lower than that could be underweight.
Tiongson says pediatricians also look for potential weight issues when a toddler's BMI percentile is over the 85th percentile -- that's the top limit of the healthy weight range. Toddlers with a BMI percentile higher than the 85th could be overweight. These children are heavier than 85% of children their same age.
And, Tiongson says, pediatricians definitely take note when a child's BMI reaches the 95th percentile. At that point, your toddler may be obese.