More than one out of five U.S. adolescents between the ages of 12 to 19 are obese and, according to a University of California San Francisco study, teens already in that range are more likely to continue to suffer with poor overall health as they get older, including type 2 diabetes and cardiovascular disease.

Even worse, those who manage to get in shape as an adult and achieve a body mass index in the normal range are still likely to fall prey to the same serious conditions as they age, simply because they were overweight in adolescence.

Youth does not make obesity any less dangerous and may in fact, set the stage for serious health consequences later on.

The Body Mass Index, or BMI, is a rule of thumb measurement based on tissue mass (muscle, fat and bone) and height. It is used to broadly categorize a person as underweight, normal weight, overweight or obese. A BMI of 25.0 or more is considered overweight, while a healthy range is 18.5 to 24.9. You can find your BMI by going to the Centers for Disease Control’s (CDC) BMI calculator and inputting your height and weight.

The study analyzed the self-reported health data from 12,300 people who were followed for 24 years (from adolescence to adulthood), as part of a national longitudinal study of health. The researchers found that a high BMI as an adolescent increased the risk of type 2 diabetes by almost 9 percent, worsened overall health by 2.6 percent and raised the chances of having a heart attack by 0.8 percent.

What made the findings of this study so striking are they showed that years later, even if participants got in shape and their BMI fell within the normal range, their health suffered the same negative consequences as if they were still obese.

In other words, youth does not make obesity any less dangerous and may, in fact, set the stage for serious health consequences later on. “Adolescent BMI is a risk factor for worsening adult health, regardless of adult BMI,” the lead author of the study, Jason Nagata, confirmed in a press statement. “Our research suggests that adolescence is an important time to optimize health and prevent early heart attacks.” The team points out that when assessing the risk of cardiovascular and chronic disease, healthcare providers need to ask about patients’ BMI history.

Even if participants who had been obese as teens got in shape, their health suffered the same negative consequences as if they were still obese.

A high BMI during adolescence can be caused by a combination of factors including genes, the kinds of food options available in a given neighborhood, metabolism, lack of sleep, endocrine disorders or other diseases. You can lower your BMI by making healthier nutritional and lifestyle choices. “Pediatricians should encourage teens to develop healthy behaviors including physical activity and balanced meals,” said Nagata, an assistant professor in the Division of Adolescent and Young Adult Medicine at UCSF.

How to Help
If your adolescent is struggling with their weight, here are some ways to help:

  • Serve breakfast. Teenagers who eat a healthy breakfast — compared with those who skip it — get more essential nutrients and have better overall eating habits.
  • Eat together. Family meals are linked to fewer poor eating habits such as skipping meals or binge eating.
  • Promote family activities. Find fun and active things the family can do together, but try not to make exercise into a punishment or a chore.
  • Limit screen time. Other than school work, it’s best to keep recreational screen time down to two hours a day.
  • Offer a fitness tracker. Some evidence suggests that wearable electronic fitness trackers may help teenagers set goals and monitor their own activity levels.

The study is published in the Journal of American College of Cardiology.