Even a cursory estimate shows how quickly

Such costs have given rise to a wellness industry that promotes healthy living now as a means of avoiding disease and expense later. The industry, which has exploded to $2 billion in annual revenue from less than $100 million a decade ago, promotes smoking-cessation and stress-reduction programs, as well as healthy-diet and daily-exercise regimens such as stretching and moderate weight training. Even a cursory estimate shows how quickly a few health measures pay off.

Lose weight. Obesity is linked to diabetes, cardiovascular disease, cancer and more. Obese people spend a third more than fit people on health services and three-quarters more on medications, according to Rand Health. The average annual out-of-pocket cost for diabetics is $454, according to an analysis of government data conducted by Nationwide Better Health, a health-management company. But those costs skyrocket to $12,000 or more for the 1 in 2 diabetics who do not carefully tend to their illness, says Nationwide. Bottom line: shed some pounds, avoid these diseases and invest the related windfall from, say, age 40 to 65--and you could pad your nest egg by up to $700,000.