A lifetime of bad eating and no exercise means your arteries are clogged, nothing you can do to change that you just live with it, and physical activity could eventually give you a heart attack as your heart fails to keep up with the new demand.

You will likely have little muscle mass, most of your body will be a bunch of layers of fat covering small weak muscles, and at age 50+ your body is simply not going to build muscle the way it used to, if at all. On the contrary, if you had built a fit muscular body early when you’re young and maintained it all your life, your body in old age would be mostly dense muscular structures, and thin layers of fat. Two old people can appear the same size but have radically different compositions underneath. Even though we lose muscle as we age, the best defense is to have plenty of muscle to spare. The muscles also help in the regulation of insulin.

And then of course there’s the issue of bones. Physical exercise and lifting weights builds strong dense bones and if you’ve neglected both then you’re plunging into old age with a bad skeletal foundation. Your bones will be brittle and hollow and more prone to breakage and unable to tolerate stress. Building strong bones takes time, it’s measured in microfractures. At 50+, you don’t have time.

With bad bones, bad muscles, and a bad circulatory system, it’s easy to see how you should be in a bed “getting some rest” instead of out doing strenuous activity where you can break something easily.