For American seniors, obesity is the new smoking

Good news: Seniors in America are living longer because they're giving up smoking.

Bad news? Older Americans are instead shortening their lives because they're obese.

Life expectancy in the U.S. is strangely lagging behind other industrialized nations — and researchers at Boston College set out to discover the reason.

The answer? Being fat is the new smoking, according to new research from Boston College's Center for Retirement Research.

In prior decades, life expectancy at age 65 in the U.S. had been lagging behind other high-income countries, particularly for women. "Going forward, smoking is no longer a major contributor to the life-expectancy gap; the real challenge is curbing obesity," the researchers found.

Many American men and women who stopped smoking after 1990, and with a 20- to 25-year lag, saw that their life expectancy improved as a result. Today, the U.S. now has one of the lowest smoking rates of high-income countries for both men and women; that was not the case for much of the 20th century. (Historically, Americans smoked more cigarettes per person than any other country, according to the center's paper.)

Smoking doesn't show up as a factor in death rates until two to three decades later.

Smoking among American men peaked at close to 80 percent in the 1940s and 1950s and began to decline steadily in the 1960s — the Marlboro Man era. After 1990, that decline in smoking began showing up in the improved data, with longer life expectancy for seniors today.

Smoking peaked more than a decade later for women, from 1980 to 2000, so the favorable effect from decreased smoking is just now showing up.

Smoking's effect on mortality was even quantifiable down to the cigarette: Each additional cigarette women smoked per capita per day reduced life expectancy 2½ decades later by 0.30 years —  or 3.6 months. In the 1980s, U.S. women purchased 2.4 more cigarettes per capita per day than women in nine other countries, suggesting a reduction in life expectancy 2½ decades later (2005) of about eight months. The comparable figure for men is six months.

So if seniors have stubbed out their smokes, what are the effects of being overweight or obese?

The direct impact of obesity on mortality is less clear-cut than smoking, but obesity — including poor diet and physical inactivity — has been linked to a higher risk of stroke, cardiovascular diseases, cancer, and type 2 diabetes.

In terms of obesity, each percentage-point increase in women who are obese reduces their life expectancy by 0.05 of a year — slightly more than half a month. In 2005, the gap in obesity prevalence between the U.S. and the nine other countries was 21.4 percentage points, suggesting obesity reduced life expectancy by almost 13 months for women. The comparable figure for men was a little over eight months.

Between 1980-2016, smoking wasn't an important factor in the U.S. shortfall for men; they had reduced their smoking substantially and cigarette sales were close to the average of other countries for most of the earlier period.

Meanwhile, obesity has increased steadily for American men and now explains about 56 percent of the shortfall in life expectancy. In Philadelphia County especially, dwellers struggle with obesity.

In the case of women, the effects of obesity weigh heavily. As of 2016, Boston College researchers estimate obesity explains almost half — or 46 percent — of the gap in average life expectancy for women.

If inactivity and obesity are the new smoking, does activity and losing weight help? Naturally, but you have to start in midlife.

Even at age 50, being overweight is associated with an increased risk of death, according to a study conducted by the National Cancer Institute, part of the National Institutes of Health, in collaboration with AARP, the nation's leading organization for people 50-plus.

And a healthy lifestyle adds years: Even after age 75, lifestyle behaviors such as physical activity are associated with longer survival — adding five years to women's lives and six years to men's. The results also held up among those older than 85 years of age and in people with chronic conditions, according to a Swedish study.