Exercise helps to prevent disease and prolong life. The Copenhagen City Heart Study found that those who exercised 2.6 to 4.5 hours per week were 40 percent less likely to die over the next 25 years than the less active people (Mayo Clinic Proceedings, August 17, 2021). Participants were 8697 healthy adults who recorded their time in leisure-time sports activities such as tennis, cycling, swimming, jogging, calisthenics, health club activities and weightlifting. Surprisingly, those who worked out more than 10 hours per week lost some of that advantage, but were still better off than the less active people. Another recent study following 2110 people for almost 11 years found similar results (JAMA Netw Open, 2021;4(9):e2124516). Those taking at least 7000 steps per day had a 50 to 70 percent lower death rate than the more sedentary group, but taking over 10,000 steps per day did not increase that advantage.
I think that both of these studies do not give you the whole picture because they did nothing to measure the level of fitness achieved by the exercisers; they looked only at hours spent exercising or number of steps. A huge study from the Cleveland Clinic that used treadmill stress tests to classify fitness levels found that the more fit a person was, the less likely they were to die (JAMA Network Open, Oct 19, 2018;1(6):e183605). This study followed more than 120,000 patients for up to 27 years, and there was no limit to the increase in benefits from improving fitness. The elite athletes (top quartile) had an 80 percent reduction in risk for death during the study period, compared to the group with the lowest fitness level (bottom quartile).
