But how do you know if your child is overweight or obese? Doctors maintain that the way to tell involves a term you may already be familiar with: BMI, or body mass index.
What Is BMI, and Why Does Your Child’s Number Matter?
BMI is a scale that defines obesity by taking body weight and height into account. Children whose weight puts them in the 95th percentile, or heavier than 95 percent of children their age, are considered obese, according to the Centers for Disease Control and Prevention (CDC). (1) Childhood obesity is a pressing issue. Data from the CDC suggest that since the 1970s, childhood obesity has tripled. In 2015–2016, about 1 in 5 kids of school age in the United States were obese. (2) “Right now, the obesity epidemic is probably the worst it’s ever been,” says Daniel Ganjian, MD, a pediatric obesity specialist at Providence Saint John’s Health Center in Santa Monica, California. He recommends that all parents focus on prevention by keeping tabs on their children’s nutrition and exercise habits. Children with family members who are overweight or obese are more likely to struggle with weight issues, too, since genetics and metabolism play a role in a child’s weight, past research shows. (3,4) Short sleep duration and community safety furthermore can affect a child’s risk. (3) But there are two factors that contribute to childhood obesity that you can control: eating habits and lack of exercise. (4) While you may rely on convenient fast foods, processed foods, sodas, packaged snacks, candy, white breads and pastas, and sugary drinks to feed your child, it’s important to keep in mind that these eating choices can result in unhealthy weight gain, according to the U.S. Department of Health and Human Services. (5) A diet high in unhealthy fat and sugar, and low in good-for-you nutrients — all of which characterizes these types of foods — can be a recipe for obesity, notes a study published in January 2015 in the British Journal of Nutrition. (6) Dr. Ganjian says eating at a restaurant or having fast food more than once a week and not eating fruits and vegetables can put you and your family at a greater risk for obesity. (4) Your child also needs to get enough exercise to ward off unhealthy weight gain. That can be tough in this day and age, when tablets, laptops, and gaming systems abound. But the more time children spend in front of screens, the less likely they are to get the exercise they need to burn off extra calories, according to the National Heart, Lung, and Blood Institute. (7) On the flip side, your socioeconomic status can affect your child’s risk of being overweight or obese, but is less controllable than other factors. Parents in low-income communities often lack the education and resources needed to provide healthy meals. Children may visit corner stores to get unhealthy snacks or eat fast food because it’s more affordable, notes a study published in December 2015 in Childhood Obesity. (8) They may also spend more time indoors if the neighborhood isn’t safe for outdoor play, according to research cited in an article published in the April–June 2015 Journal of Family Medicine and Primary Care. (9) Working with your child’s pediatrician to identify healthy-eating and exercise strategies can help reduce their risk for childhood obesity. Your child’s weight can affect more than just their physical appearance. Just like adults, children can struggle with stress, anxiety, and depression. If they aren’t taught healthy ways to cope with these feelings, they can develop an unhealthy relationship with food. (4) The CDC recommends using BMI percentile to measure children and young people ages 2 years to 20. (10) Each time your child goes to the pediatrician, his or her height and weight is taken and the BMI percentile is plotted on a graph that compares your child’s number with those of other children the same age, height, and sex. This is how to interpret the results, according to the CDC:
Underweight: less than 5th percentileHealthy weight: 5th percentile to less than 85th percentileOverweight: 85th percentile to less than 95th percentileObese: equal to or greater than 95th percentile
What BMI Is Considered Overweight for a Child?
A child whose BMI falls between the 85th and 95th percentiles is considered overweight, while children at or above the 95th percentile (meaning their weight is higher than that of 95 percent of their peers) qualify as obese. (1) This chart compares a child’s BMI (calculated as weight in kilograms divided by height in meters squared) with his or her age. The red portion is associated with childhood obesity.
How to Calculate Your Child’s BMI Percentile on Your Own
To calculate your child’s BMI percentile on your own, Marisa Censani, MD, a pediatric endocrinologist at New York-Presbyterian Komansky Center children’s hospital in New York City, recommends using online resources, like apps and calculators. For example, the CDC has an online BMI calculator that allows you to plug in a child’s age, sex, height, and weight. You’ll need to take accurate height and weight measurements first. (11) To measure your child’s height: To measure your child’s weight: Ganjian doesn’t advise waiting for BMI to get into the trouble zone before you make healthy lifestyle changes. Whether you’re overweight or not, everyone in the household can benefit from eating nutritious food and exercising. “There are times when we’ll start an intervention before a kid gets to the 85th percentile because BMI is going up quickly,” he says They include:
Measuring skinfold thicknessDoing underwater weighingTaking waist circumferenceUsing dual energy X-ray absorptiometry (DEXA) or a whole-body scan of bone and tissue
Although methods like DEXA and skinfold measurements are more accurate than BMI, BMI can provide a reasonably correct number to go by when these aren’t available, according to a study published in April 2016 in Public Health. (12) One study published in July 2017 in JAMA Pediatrics suggests a formula called tri-ponderal mass index (TMI) may help accurately measure children’s BMI percentile. It’s calculated by weight divided by height cubed. Researchers found TMI to be more accurate in measuring body fat levels in children and teens ages 8 to 17 when compared with BMI. (13) “Children with a body mass index percentile at the 95th percentile [or above] have a greater chance of maintaining obesity into adulthood,” says Dr. Censani. (1,11) Immediate potential health consequences of a high BMI percentile in children include: (1) Prediabetes or type 2 diabetes If poor eating habits and weight gain are left unchecked, kids can develop prediabetes or type 2 diabetes at an early age. The Mayo Clinic notes that the obesity epidemic has fueled a rise of type 2 diabetes diagnoses in children, and 40 percent of this group is asymptomatic. (14) Sleep apnea Sleep apnea causes breathing to stop and start irregularly during sleep. A BMI suggesting obesity puts children at a higher risk for developing the condition. If left untreated, sleep apnea can cause complications with the heart and lungs over time. Asthma Children with a BMI showing they’re overweight or obese are at a higher risk of developing asthma than children who have a normal BMI. Long-term potential health consequences of a high BMI percentile in children include: High blood pressure and high cholesterol Both of these conditions develop over time and put you at risk for heart disease. Obesity during childhood can increase the likelihood of having heart problems later in life. (9) Nonalcoholic fatty liver disease When fatty deposits build up in the liver, it causes scarring that may eventually lead to liver damage. Cancer A diet that lacks proper nutrients and puts extra strain on the body may also increase your child’s risk of developing cancer. Arthritis Carrying extra weight puts pressure on the joints, which can lead to conditions like osteoarthritis over time. Three things factor in the development of these medical problems: age, genes, and weight, says Stephen Pont, MD, MPH, a pediatrician and the medical director for the Texas Center for the Prevention and Treatment of Childhood Obesity in Austin. The only one we can work on is weight, he says. In addition to physical health complications, children who are overweight or obese may also face mental health issues. They’re more likely to experience ailments such as depression, guilt, and anxiety, says Dr. Pont. A policy statement by the American Academy of Pediatrics published in November 2017 in Pediatrics, suggests that these mental illnesses are associated with the stigma that obese or overweight adolescents can face. (15) About 71 percent of teens seeking weight loss treatment reported being bullied about their weight within the past year, the statement reads. (15) “If a child is a long way away from a healthy weight, it took them a while to get here, so we need to be patient,” says Pont. That means starting with small changes and gradually working your family up to a healthier diet and more exercise. Including children in that process helps them get invested and can improve the likelihood that healthy habits will stick. For example, you could ask them which healthy habits they want to work toward first and build from there. Consider offering nonfood rewards, like a trip or a new toy, for achieving the goals you set together. Kids generally eat what’s in the house, so stocking the pantry with healthy options can help them stay on track, according to a study published in January 2013 in the International Journal of Behavioral Nutrition and Physical Activity. (16) Keep (17,18)
Fresh fruits and vegetablesLean proteins, such as chicken, fish, and tofuWhole grains, like brown rice and whole grain breadsLow-fat dairy
Ditch (17,18)
Packaged and processed snacks, including chips, cookies, cakes, and candySoft drinks and sugary juice
Increasing exercise time is also an important step. The CDC recommends children get at least 60 minutes of moderate to high-intensity physical activity each day. (19) Ganjian uses the 5-4-3-2-1-0 system, which stands for:
5 daily fruits and vegetables4 compliments per day3 portions of calcium per dayNo more than 2 hours in front of a screen daily (unless it’s homework related)1 hour or more of exercise per day0 sweet drinks (including juice) daily
Another habit to change is how many meals the family is eating at restaurants or ordering out each week. Instead, focus on cooking healthy meals at home. When you’re preparing the food, you have control over the nutritional content. “The key is for families to support dietary changes for their children and to incorporate these changes for the entire family," says Censani. “Encouraging and supporting children as they try new foods and helping prepare meals will give them a healthier approach to their dietary choices.” Additional reporting by Moira Lawler.
