Fit is not healthy
Being physically fit does not necessarily mean you are healthy
That's the more precise way to say it. Yes, you can be physically fit and healthy. But you could also be quite healthy but not necessarily that "fit." You could also be quite fit and very unhealthy. In addition, not uncommonly, a strong commitment to fitness, like running marathons, can contribute to unhealthy conditions.
This is what Wikipedia has to say about Jim:
"James Fuller Fixx (April 23, 1932 – July 20, 1984) was an American who wrote the 1977 best-selling book The Complete Book of Running. He is credited with helping start America's fitness revolution by popularizing the sport of running and demonstrating the health benefits of regular jogging."
Jim Fixx was quite fit when he died at age 52.
Wikipedia went on to say:
"Fixx died on July 20, 1984 at age 52 of a heart attack, during his daily run on Vermont Route in Hardwick. The autopsy, conducted by Vermont's chief medical examiner, Dr. Eleanor McQuillen, revealed that atherosclerosis had blocked one coronary artery 95%, a second 85%, and a third 70%.
"In 1986 exercise physiologist Kenneth Cooper published an inventory of the risk factors that might have contributed to Fixx's death. Granted access to his medical records and autopsy, and after interviewing his friends and family, Cooper concluded that Fixx was genetically predisposed—his father died of a heart attack at 43 after a previous one at 35, and Fixx himself had a congenitally enlarged heart—and had an unhealthy life: Fixx was a heavy smoker before beginning running at age 36, had a stressful occupation, had undergone a second divorce, and gained weight up to 214 pounds (97 kg)."
NEAT and some exercise will support good health
NEAT or "non-exercise activity thermogenesis" is the energy expended for everything we do that is not sleeping, eating or sports-like exercise. However, in no way does exercise, especially a lot of it, necessarily guarantee that we will be healthy. Although several factors contribute to good health, what we eat and don't eat is sine qua non of good health. You cannot make up for poor eating habits with exercise. For example, while running up to 80 miles a week and appearing to be in incredible physical condition, Jim Fixx continually ate fast food and junk food. He’s also rumored to have often consumed excess amounts of sugar.
HIIT (high intensity interval training)
If you love exercise and have fun putting in the traditionally recommended 150 minutes a week of moderate exercise, that fine. However, scientific tests have demonstrated that three minutes a week (20 seconds a hit) of super intense exercise will deliver the same cardiovascular health results.
The dangers of fitness
Over my 35+ years as a life coach (since 1987), I have noted that several friends and a larger number of clients who were into long and intensive exercise routines, ended up incurring injuries that became chronic indefinite disabilities, for example, knee injuries. The dictum, "no pain, no gain" had been one of the most toxic ideas to become embraced by the general public.
Nutrition, Fitness, Sleep (a toolkit)