It's not always easy to quantify how much improving your fitness will affect your health, but that's exactly what researchers at the University of South Australia attempted to do. What they discovered is increased cardio fitness cuts the risk of dying from any cause by nearly 20 percent.

Specifically, using a meta analysis of data from 199 different studies, scientists found for every 1-MET increase in cardiorespiratory fitness, a person can reduce their risk of death from all causes by 11-17 percent and cut the risk of heart disease by 18 percent. MET is short for metabolic equivalent and it equates to the amount of oxygen consumed by the body while sitting at rest.

"Cardiorespiratory fitness (or CRF) is your ability to perform physical activity for a long period of time like running, cycling, and swimming," researcher Grant Tomkinson said. "In this study we found that high levels of cardiorespiratory fitness reduce the risk of dying early from any cause.

"We summarized the evidence linking CRF to numerous health outcomes and found that those with low levels of CRF are far more likely to die early or develop chronic conditions like heart disease later in life."

Heart disease is the leading cause of death in America as well as Australia. Reducing it's impact has been a priority of researchers for a long time, which makes this study relevant in both countries and beyond.

"For most people, a 1-MET increase in CRF can be achieved through a regular aerobic exercise program," Tomkinson said. "The message is quite simple: if you do a lot of 'huff and puff' exercise, then your risk of dying early or developing diseases in the future is reduced. If you avoid exercise your health may suffer."

"Clearly, cardiorespiratory fitness is as an important factor for good health," Dr. Justin Lang said. "If you are already exercising, this is good news; but if you know you need to up your fitness and movement, then this is a timely reminder. People can make meaningful improvements through additional moderate physical activity, such as brisk walking, at least 150 minutes a week. And as they improve their fitness, their risk of death and disease will decline."

Click here to read more in the British Journal of Sports Medicine.