Is your kid fat?

It’s estimated that a third of kids in America are overweight and as many as one-fifth are obese. Yet, according to one study, most parents don’t realize their child’s weight is a problem. But how could that be? According to one expert from the American Academy of Pediatrics, society has gotten accustomed to seeing children being heavier so it has become harder to spot a problem.

But the truth is the extra weight is causing our kids to develop early signs of heart disease. Research out just this week looked at a group of overweight and obese kids with high cholesterol and found the arteries of an obese 10-year-old had the same amount of plaque as a 45-year-old's!  The kid’s arteries looked as if they were more than 30 years older than their actual age! This is significant because doctors agree we are all as old as our arteries. The condition of your heart and blood vessels are often more important than your actual age in terms of preventing diseases later on.

How do you know if your kid is overweight or obese? There is no easy rule of thumb because kids vary so much in height and body types during childhood. But according to the Centers for Disease Control and Prevention, the average 5-year-old should weigh about 40 pounds, the average 8-year old-about 55 pounds and an average 10-year-old should weigh about 70 pounds.

Won’t my pediatrician tell me if there my child’s weight is a problem? Your pediatrician may not always bring it up, so you need to raise the question during the appointment. According to the American Academy of Pediatrics, parents whose children live relatively sedentary lifestyles, eat at restaurants often or have a family history of obesity should ask their pediatrician to address BMI at every appointment.

What can I do to help my child lose weight? For most children, the answer is lifestyle overhaul. Let's face it, kids today prefer watching TV and playing video games. As parents, we need to make it a priority to develop fun activities to get our kids moving. Also, just say no to fast food! Dietitians estimate that every meal eaten out has double, sometimes triple, the caloric intake of an at-home meal. And be careful of empty calories found in sugary drinks. Juice boxes can be deceiving and soda is loaded with over 100 calories and up to 40 grams of sugar! Making simple changes such as cutting out liquid calories is an easy way to make a significant difference in their diet.

The bottom line is to pay attention to our children's weight and help provide an environment that fosters healthy habits. Because the habits they form as children, often carry over into adulthood.

Be sure to tune in to Dr. Sanjay Gupta every weekend on "HOUSE CALL." You'll find the answers to your medical questions Saturday and Sunday at 8:30 a.m. ET on CNN.