Is hefty the new healthy?

Americans have been getting heavier since the Civil War, and it's safe to say some of the added weight reflects improvements in health. Better nutrition, improved housing, control of infectious diseases — they all helped fill out the American physique, and add some inches to it as well. But in the 1980s and 1990s, the long-term trend of adding pounds took off, and we found ourselves in the midst of an obesity epidemic.

There was some good news early in 2010 when government researchers reported that the relentless rise in the proportion of Americans who are obese has leveled off since 2000, and especially so among women. That's fortunate, because an analysis published in The New England Journal of Medicine late in 2009 predicted that if obesity prevalence were to continue to climb as it did in the epidemic years, almost all the health gains from the reduction in smoking would be wiped out by the heart attacks, strokes, diabetes, and joint problems caused by heftiness.

Some health benefits?

But there's been some doubt rattling around about whether we really should be so concerned about being heavy once we're older. A scattering of observations and studies over the years have pointed to there perhaps being some benefits to heaviness — benefits that might be particularly germane to life in the later decades. Bigger people tend to have thighbones (femurs) with higher bone mineral density readings, an indication of bone strength. A number of studies show that heavier women are less likely to break a hip than women who would generally be considered closer to a healthy weight. And some data suggest that overweight, and even obese, people do better than their normal and underweight counterparts after coronary artery bypass surgery.

Three recent studies

The possibility that the usual rules don't apply in old age has been batted around awhile. A report in The Journal of the American Geriatrics Society (JAGS) in 2001 made the case that high body mass index (BMI) wasn't predictive of mortality in people 70 and older. BMI is a way of taking height into account when measuring weight.

Lately, JAGS has published additional findings along the same lines. In 2008, British researchers reported in the geriatrics journal that excess body weight in people ages 65 and older was not associated with mortality. The not-so-minor catch: obesity was correlated with impaired physical function.

In 2009, Israeli researchers reported results of a study of Jerusalem residents at ages 70, 78, and 85. At all three ages, women who were overweight or obese were less likely to die in the follow-up period, which varied, than women with BMIs in the "normal" range of 18 to 24.9 that's generally considered the healthiest. Interestingly, BMI didn't seem to affect the survival chances of the men.

Australian investigators added results to the pile in 2010. Their study of 9,000 Australians between the ages of 70 and 75 showed that the risk of dying during 10 years of follow-up was lowest for those in the overweight category.

So should we change course and aim to get a little fatter in our old age for health reasons? Absolutely not. For one thing, studies of weight in old age run into the problem that people lose weight when they're sick, often well before a diagnosis, so being thin can seem to cause illness when it's really the other way around. Researchers make adjustments to take "reverse causation" into account, but it lingers as a problem.

Besides, the results from these three studies are hardly the final word on the subject of BMI, weight, and mortality. Other studies, including an impressive pooled analysis of 57 studies published in 2009 in The Lancet, show a correlation between high BMI and higher death rates, even among older people.

Watch the waist, too

Rather than being an endorsement for getting fat, these findings may help us to pay attention to our waists, in addition to our weight.

For most of us, the plain fact is that weight gain when we're adults is an indication that we are, indeed, getting fatter and therefore very likely at greater risk of suffering from a long list of diseases.

It does get a little more complicated in older age. We lose muscle mass and bone density, so while we may weigh the same as we used to, or even less (and congratulate ourselves on being thin), we may actually be lugging around more fat tissue. So we need to keep an eye on our waist size, not just our weight, especially after about age 50. Waist size is a fairly accurate reflection of how much visceral fat we've accumulated in our abdomens. And visceral fat is the metabolically active form of fat that causes so much harm.