Attention, college students: Get off that shuttle bus and start walking to class.

You’re already eating a diet of mainly beer and pizza, staying up all hours of the night, and living in cramped, potentially germ-infested dorms. The last thing on your mind is whether you’re setting yourself up for future cardiovascular disease or Type 2 diabetes.

Now might be a good time to start thinking about it…

A new study by Tufts University scientists found that body fat percentages are not the only precursors to health problems later in life. A person's physical fitness may matter a lot more -- at least when it comes to developing cardiovascular disease or diabetes.

Motivated in part by the astounding growth rate of obesity amongst college students -- approximately 31% of U.S. college students are overweight or obese -- researchers at Tufts' Friedman School of Nutrition Science and Policy tracked the health and health-related behaviors of 564 male and female college students over a nine-year period. They tracked body fat, fitness level and risk factors such as cholesterol and blood glucose levels.

Their findings: Students who were physically fit -- regardless of their body fat content -- had lower blood triglycerides, higher HDL (the "good" cholesterol). That effect was especially marked in women.

The fitter students also had lower blood glucose levels, an effect that was especially marked in men.

The findings are important, says Jennifer M. Sacheck, one of the study authors, because they suggest that the roots of later disease may be laid down early. "Because most of these health problems show up more often later in life, most studies have focused on adults, and very few have been done on college populations or anyone younger," she said in a phone interview.

However, she added, because students won't be tracked through their lives, there's no way to guarantee that heart disease and diabetes actually will develop in those students who look like they're heading that way.

The study does suggest that maybe we should change the way we think about health -- basing it not so much on weight and body fat composition, but more on physical fitness and the frequency of exercise.

And, Sacheck says, the message has particular importance for college students who are known to be more careless and reckless with their health than other age groups:

"In college, you think you're invincible, at the peak of your health, and that your body can handle anything. But my message [in this study] is that even at this age your body is susceptible."

For those who have long cursed the Body Mass Index, which stratifies a person's health level based on weight and height equations, this study is heartening. Perhaps it's time to stop worrying about the number on the scale and whether you can still fit in the jeans you wore in high school, and instead pat yourself on the back for running each morning. It might seem paradoxical, but being physically active and a bit pudgy might be better than skinny and unfit.