It is no secret that a growing percentage of Americans can be considered overweight or obese, and that includes children. The number of kids between the ages of 2 and 19 who can be categorized as obese has now grown to 20 per cent, or one in five.

“Essentially, from the 1970s to the ’90s, there was a huge increase in the number of kids who are considered to have obesity … too high a body weight for their own good,” Dr. Jack Yanovski, a pediatric endocrinologist at the National Institute of Child Health and Human Development, told CNN Chief Medical Correspondent Dr. Sanjay Gupta on his podcast Chasing Life.

With children, doctors define obesity a bit differently than they do with adults. Children’s body mass index — imperfect as the measurement is — is calculated in the same way (weight in kilograms divided by height in meters squared), but the threshold for obesity is not a BMI of 30 or above.

Instead, kids are compared with others of the same age and gender. If their BMI is equal to or greater than the 95th percentile (if they are bigger than 95 out of 100 other kids their age and gender), then they are considered to have obesity. Severe obesity is having a BMI equal to or greater than the 120th percentile.

In addition to the social stigma — being considered heavy is one of the most common reasons that kids are bullied at school — carrying around extra weight can lead to present and future health problems.

“Most people who are heavy by the age of five or six will tend to continue to have problems with body weight throughout adolescence and into adulthood,” Yanovski said.

The negative health effects will have a chance to build up. “We know that those individuals will therefore accrue the greatest risks from their higher body (fat) because they’re going to continue to have high body weight throughout the years,” he said.

Think it’s time to discuss weight with your child? Talking to a child of any age about weight is a delicate matter for parents and pediatricians. After all, children are growing, their bodies are changing, and they are supposed to gain weight as they grow. Knowing what is healthy and appropriate, and socially and personally acceptable, can feel subjective to a parent and child.

“Generally, you should start with your health care provider,” Yanovski said. “Remember, kids come in all different sizes and shapes. And their caloric demands will be very different based on where they are in their growth cycle. So have them measure and examine your child (to) see if they think it’s a medically important condition.”

If parents come down too hard, kids can get depressed or resentful, feel stigmatized or singled out; some might even develop eating disorders to lose weight.

“Parents have to be alert and responsive to their children,” Yanovski said, “and mostly not shaming them about their relationships with food to try to avoid these problems.”

Here are Yanovski’s top five tips:

Tread lightly

Don’t come in like a bulldozer with a “parent knows best” attitude.

“Be humble and mindful of how you speak because there’s often bias and weight stigma,” Yanovski said. “Your children should feel comfortable and safe sharing their concerns or struggles. If you need to make changes or consider therapies, keep in mind that decision-making is a shared process.”

There’s no one ‘right’ body size

Children are a work in progress, and growth spurts are normal.

“Remember there’s a range of healthy weights and that children are supposed to grow, especially during puberty,” Yanovski said. “Your child’s health care providers can discuss with you what’s appropriate for your child.”

Hit the easy button

Make healthy choices the default.

“Create a healthy environment by considering what foods and snacks are available in the home,” Yanovski said. “For example, when children come home hungry from school, offer a plate of fresh fruit and vegetables. For meals, don’t offer a family-style serving at the table, but plate everyone’s portions in the kitchen.”

Don’t use cake as a carrot

Food should not be used as an incentive.

“Don’t make food the ultimate reward for behavior, grades or chores,” Yanovski said. “Don’t make highly palatable foods the reward for celebrations. You can substitute activities or other nonfood rewards.”

Steady as they grow

A child’s body is in a constant state of flux, but parents’ attitudes should aim to be stable.

“Be consistent with your expectations,” Yanovski said. “When you’re inconsistent, switching between lax and overly severe, that’s a problem.”

He noted that parents often are disciplinarians. “But we have to avoid going overboard in that direction,” he said, “so that we can remain available to our kids and help them work their way through a very difficult time in their lives.”