Your fitness age is based on the body’s ability to utilize oxygen, with the best measures coming from individuals hooking up to a respiration mask and hitting the treadmill. If you’re 25 years old, then it will tell you whether your fitness level is of a 20 year-old marathoner or a sedentary 50 year-old man. How efficiently the body is utilizing available oxygen, scientists would then measure that.

But now, there’s a better way to approximate our fitness age, simply by taking an online test, after researchers studied over 5,000 Norwegians. According to New York Times, the researchers took about a dozen measurements, including HDL and total cholesterol…