What Does Your Child’s BMI Mean for His or Her Health?
Being overweight or obese can put your child at risk for future health issues, such as heart disease and type 2 diabetes. Learn how to calculate your child’s BMI percentile and help them hit a healthy number.
American children are increasingly tipping the scale, and the extra weight is putting them at risk for immediate and future health complications, including depression, type 2 diabetes, and heart disease.
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, fat, 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. (1)
Childhood obesity is a pressing issue: The number of 6- to 11-year-olds whose BMI corresponded to, or was higher than, the CDC's 95th percentile growth charts was 4.2 percent between 1963 and 1965; that number rose to 15.3 percent between 1999 and 2000. (2)
“Right now, the obesity epidemic is probably the worst it’s ever been,” says Daniel Ganjian, MD, pediatric obesity specialist at Providence Saint John’s Health Center in Santa Monica, California. He recommends all parents focus on prevention by checking their children’s nutrition and exercise habits.
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What Are the Different Causes of Obesity in Children?
Various factors may contribute to your child’s weight, including family history, mental health issues, socioeconomic status, and lifestyle habits. Some of these are within your control, while others aren’t.
Children with family members who are overweight or obese are more likely to struggle with weight issues as well. (3) But the most common contributors to the obesity epidemic are poor 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. (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. (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)
Making sure your child gets enough exercise is also key for warding off unhealthy weight gain. That can be tough in this day and age, when tablets and laptops abound. But research suggests 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. (7)
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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. They may also spend more time indoors if the neighborhood isn’t safe for outdoor play. (8, 9)
Working with your child’s pediatrician to identify healthy-eating and exercise strategies can help reduce their risk for 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)
What’s BMI Percentile? How Measuring Body Fat Is Different in Kids
As an adult, you can calculate your BMI by taking your body weight in pounds, and diving that by the value of your height in inches squared, and then multiplying that value by 730. But because children and teens are still growing, their BMIs are plotted on a graph as percentiles. Each value is referred to as a BMI percentile. (1)
The Centers for Disease Control and Prevention (CDC) recommends using BMI percentile to measure children and young people ages 2 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 to other children of the same age, height, and sex.
This is how to interpret the results, according to the CDC:
- Underweight: less than 5th percentile
- Healthy weight: 5th percentile to less than 85th percentile
- Overweight: 85th percentile to less than 95th percentile
- Obese: equal to or greater than 95th percentile
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 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:
- Have your child take off shoes, hats, or hair accessories.
- Stand them on a flat floor against a flat wall with no floor molding.
- Make sure their legs are straight and their arms are at their sides with level shoulders.
- Have your child look straight ahead. Their line of sight should be parallel with the floor.
- Your child’s body (head, shoulders, butt, and heels) should be flat against the wall.
- Using a flat surface, make a right angle on the wall and lower the item until it reaches the top of the child’s head.
- Make a mark on the wall where the bottom of the flat surface touches the top of your child’s head. Then use a measuring tape to measure from the bottom of the floor to the mark.
To measure your child’s weight:
- Use a digital scale that’s placed on hard, even flooring.
- Have your child take off their shoes and any heavy clothing, and stand with both feet in the center of the scale.
- Record their weight as it appears on the scale to the nearest decimal point.
Ganjian doesn’t always advise waiting for BMI to get into the trouble zone before making lifestyle changes. Whether you’re overweight or not, everyone in the household can benefit from eating healthy 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.
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Other Options for Measuring Your Child’s Body Fat
You can measure your child’s body fat in other ways, but some of these approaches can only be done in a medical setting due to the tools they require. If your child’s BMI percentile is in the overweight or obese range, your doctor may recommend additional measurements. (1)
- Measuring skinfold thickness
- Doing underwater weighing
- Taking waist circumference
- Using dual energy X-ray absorptiometry (DEXA) or 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. (12)
One study 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)
The Health Risks Associated With Childhood Obesity
When it comes to your child’s health, the earlier he or she learns to develop healthy eating and exercise patterns, the better. There are a variety of health risks that come from childhood obesity. Some may take years before they show up, while others can be seen much earlier. If obesity continues into adulthood, the risk for health complications goes up. (4)
“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. (11,14)
Immediate potential health consequences of a high BMI percentile in children include: (14)
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. (15)
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)
RELATED: What to Know About the American Heart Association’s New Blood Pressure Guidelines
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 go into developing medical problems: age, genes, and weight, says Stephen Pont MD, MPH, medical director of the office of science and population health at the Texas Department of State Health Services 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. (16)
Weight stigma in American society may be a key contributor to these feelings. One study found that 71 percent of teens seeking weight loss treatment reported being bullied about their weight within the past year. (16)
How to Make Healthy Changes to Your Child’s Diet and Lifestyle
The good news is that, in most cases, the conditions listed above can be prevented or reversed once a child returns to a healthy weight. (9) But it does take work, and often changes have to be made in the entire household.
“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. (17)
- Fresh fruits and vegetables
- Lean proteins, such as chicken, fish, and tofu
- Whole grains, like brown rice and whole grain breads
- Low-fat dairy
- Packaged and processed snacks, including chips, cookies, cakes, and candy
- Soft 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. (20)
Ganjian uses the 5-4-3-2-1-0 system, which stands for:
- 5 daily fruits and vegetables
- 4 compliments per day
- 3 portions of calcium per day
- No more than 2 hours in front of a screen daily (unless it’s homework related)
- 1 hour or more of exercise per day
- 0 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.
Video: Watch: What Does Your Child’s BMI Mean?– Healthfirst Healthy Living
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