A new study suggests that it’s not as harmless to be unhealthy during the teenage years as researchers once believed. According to a report from Reuters, scientists studying a population of young men from Sweden have found that low cardiorespiratory fitness and weak muscle strength can lead to the development of type 2 diabetes later in life, regardless of body weight.

According to study lead author Dr. Casey Crump, from the Ichahn School of Medicine at Mount Sinai in New York City, “Not only were both low aerobic and muscular fitness linked with a higher long-term risk of diabetes, but this was true even among those with normal body mass index.”

The study suggests that risk factors for diabetes amplify each other. The combination of poor aerobic and muscular fitness were found to up the risk of type 2 diabetes more than each did individually, suggesting a synergistic effect.

The study pulled data from over 1 million military conscripts in Sweden between 1969 and 1997, all of whom were 18 years old. The men had no history of diabetes at the age of 18.

As researchers followed these men throughout their lives until 2012, they identified those who had developed type 2 diabetes.

Upon further analysis of the massive data pool in the study, scientists found that about 34,000 men, roughly 2 percent of the sample, were diagnosed with type 2 diabetes sometime until the end of the follow-up period. Half of the diagnoses occurred after age 46.

The researchers found that men who were the least physically fit as teenagers were three times more likely to develop type 2 diabetes than their counterparts with better measures of aerobic and muscle strength, even in men who had a normal body mass index and otherwise seemed healthy.

“This study showed that fitness traits were important for the prediction of future diabetes at any body weight so it should not be ignored, wrote researcher Peter T. Katzmarzyk in an editorial accompanying the study.

The study, published in the Annals of Internal Medicine, can be found here.