Kids’ snacks can be healthy — bananas, apples, carrot sticks and hummus — but unfortunately, new research shows that unhealthy, junk food snacking is taking over children’s diets, constituting 27% of total calories consumed. This is bad news for the nation’s childhood obesity trends, with the ranks of overweight kids (17%) continuing to grow.

Looking over dietary intake data for 31,337 kids of various ages over the past three decades, University of North Carolina researchers found that while roughly three-quarters of kids snacked regularly back in the 1970s, now virtually all kids (98%) munch outside of mealtimes. The real bad news is that this universal snacking consists primarily of junk food: chips, crackers, cookies, sweets and soda/sweetened drinks. For teens, this adds up to nearly 700 calories a day — enough to pack on over 70 pounds a year, if not burned off with activity

Excess pounds take a toll on growing bodies, increasing the risk of joint disorders, breathing constriction, emotional difficulties, more earaches — even impaired mental ability and absenteeism. Junk food harms health not just by contributing to obesity: Research suggests that sugar is addictive and may increase kids’ future likelihood of trouble with the law. Junk food consumption is also linked with higher rates of depression — while salty snacks and sodas specifically spike kids’ blood pressure, aging their arterial systems.

Published April 1, 2010