You may have assumed this or it may seem like you heard it before, but researchers say they are confirming this for the first time. Scientists at the Hospital del Mar Research Institute in Barcelona say there is a direct link between being physically fit and disease prevention.

Until now, researchers say there was no scientific evidence to prove the theory that being physically fit improves your health and reduces your risk of becoming ill. They published their findings in the journal Medicine & Science in Sports & Exercise.

"Our study results indicate that there is a potentially causal effect between good physical fitness—through good cardiorespiratory fitness—and good health," said researcher Eleonora Fornara.

The team reached that conclusion by studying the association between higher cardiorespiratory fitness as defined by the body's ability to respond well to physical exertion and the occurrence of more than 700 health conditions for which genetic information was available.

Results were validated in a two-phase analysis to avoid false positive and it was ultimately narrowed to 34 conditions. "For the first time, we have been able to establish a potential direct cause-and-effect relationship between being fit and numerous diseases through complex genetic analyses," Fornara stated.

For instance, the study showed individuals with a high genetic predisposition to being physically fit have a lower risk for a range of cardiovascular conditions such as a certain type of ischemic stroke. They also have less arterial stiffness and lower diastolic blood pressure.

Better health in terms of metabolic and inflammatory markers were also visible as well as less weight and excess body fat. The study participants also had a reduced risk of developing diabetes and asthma along with improved bone health and better liver function.

"Our findings reinforce the evidence that engaging in physical activity and maintaining good physical fitness has a preventive effect on our health," said fellow researcher Dr. Marta Hernández.

Dr. Álvaro Hernáez added, "We have verified the observational evidence available until now and demonstrated that there is a cause-and-effect relationship between good physical fitness and good health. Therefore, we can say that recommendations encouraging people to improve their physical fitness are supported by scientific evidence, and we can promote public health actions and primary care recommendations—because it works."

Click here to read more in the journal Medicine & Science in Sports & Exercise.