Obesity increases your risk for heart disease and stroke, (diabetes), and even forms of cancer. So it’s probably a good idea to get in the habit of eating right and exercising while you’re still young. But teens get mixed messages about what’s a healthy body weight. They’re bombarded with (unrealistic) images of ultra-skinny celebrities and models, while also seeing media coverage of obesity that includes photos of those who are exceptionally obese.

So a group of researchers in the U.K. wanted to know, do British teens have an accurate sense of where they fall along the weight scale?

They examined data from nearly 5,000 13- to 15-year-old collected between 2005 and 2012 by what’s called the Health Survey for England. Of the group, nearly three-quarters were normal weight. Twenty percent were overweight, with seven percent obese.

The survey included asked this question for that age (group): “Given your age and height, would you say that you are about the right weight, too heavy, or too light?”

Despite the thin-celebrity-saturated culture, 83 percent of normal weight adolescents thought they were, in fact, a healthy weight. Not (surprisingly), the data changed by gender, 11 percent of normal-weight girls thought they were too heavy, compared to just four percent of boys.

But the bad news: nearly forty percent of the overweight and obese teens did not self-identify as “too heavy.” Overweight girls recognized the issue more than boys did—nearly half the boys did not think that they were too heavy. The (study) is in the International Journal of Obesity.

The researchers say the data on overweight teens, particularly boys, “may have implications for the future health and wellbeing of young people,” and that overweight teens are substantially more likely to become (overweight) adults. Recognizing that there’s a lack of awareness among some teens could be a first step toward a healthier future.