Exercising and quitting smoking almost completely canceled the overall negative effects of obesity. In other words, being overweight barely mattered. Though it can be a struggle, giving up smoking is perfectly possible. We all know lots of people who have successfully quit. And exercise is not really that hard a thing to do, at least not as I mean it.
Activity is a better word.
As far as longevity goes, thirty minutes of brisk walking five times a week gives maximum benefit. Longer, more vigorous workouts certainly can add to fitness and sense of well-being, but they do not increase life span. And even less intense exercise, at the level of a few minutes of walking, taking a couple of flights of stairs instead of the elevator, gardening and carpentry, all counts towards improving the odds of living to see your great-grandchildren.