‘Obesity paradox’ solved?

Except that obesity is a symptom, not a disease.

Media release below.


Old age offers no protection from obesity’s death grip

Getting older increases Americans’ risk of death from excessive BMI, finds new study, correcting flaw in earlier ‘obesity paradox’ research

Obesity kills, giving rise to a host of fatal diseases. This much is well known. But when it comes to seniors, a slew of prominent research has reported an “obesity paradox” that says, at age 65 and older, having an elevated BMI won’t shorten your lifespan, and may even extend it. A new study takes another look at the numbers, finding the earlier research flawed. The paradox was a mirage: As obese Americans grow older, in fact, their risk of death climbs.

Ryan Masters, PhD, and Bruce Link, PhD, at Columbia University’s Mailman School of Public Health, in collaboration with Daniel Powers, PhD, at the University of Texas published the results online in the American Journal of Epidemiology.

The researchers argue that past studies of longevity and obesity were biased due to limitations of the National Health Interview Survey, or NHIS, which provides information on obesity. The survey excludes individuals who are institutionalized, such as in a hospital or nursing home—a group largely made up of seniors. Consequently, the data is overrepresented by older respondents who are healthy, including the relatively healthy obese. What’s more, many obese individuals fail to make it to age 65—and thus do not live long enough to participate in studies of older populations.

“Obesity wreaks so much havoc on one’s long-term survival capacity that obese adults either don’t live long enough to be included in the survey or they are institutionalized and therefore also excluded. In that sense, the survey data doesn’t capture the population we’re most interested in,” says Dr. Masters, a Robert Wood Johnson Foundation Health & Society Scholar at Columbia’s Mailman School and the study’s first author.

In his analysis Dr. Masters matched NHIS data on obesity with corresponding records in the National Death Index using data from close to 800,000 adults surveyed between 1986 and 2004. Next he performed statistical adjustments to account for the survey selection biases. The result: risk for death from obesity increases with age.

The finding jibes with countless medical studies that document how obesity takes a cumulative, even compounding toll on the human body. (Exponents of the obesity paradox have explained their counterintuitive results by suggesting that obesity’s extra padding protects seniors from fall-related injuries and provides energy reserves during illness.)

“This study should put to rest the notion that it’s possible to ‘age out’ of obesity risk, and provides a powerful counterfactual against those who say concern over obesity is overhyped,” says Dr. Link, a professor of Epidemiology and Sociomedical Sciences at the Mailman School.

Going forward, Dr. Masters has set his sites on another possible reason behind the obesity paradox—that some of the older obese captured in NHIS data only put on extra weight later in life.

“The recent obesity epidemic hit all age groups at the same time, meaning many of the elderly obese only gained their excess weight in the last 10 years or so,” Dr. Masters says. “To account for this fact, I will take a page from studies of cigarette smokers by looking at ‘life years’ to measure how long someone has been obese rather than whether or not they happen to be obese at the time of a single snapshot survey.”


2 thoughts on “‘Obesity paradox’ solved?”

  1. First, everyone’s risk of death increases as one gets older. Each day you increase your chances of developing cancer or being hit on the head by a meteorite or having a heart attack — and that’s true regardles of how healthy and careful your lifestyle is. By the time you get to be 114, your risk of death is nearly 100%.
    Second, “obesity wreaks havoc” is a scare phrase with little rigor. “Obesity” defined by what measure? We have statistical measures of weight distributions (BMIs that in the high teens, mid-twenties, high twenties and into the thirties), but those BMIs correlate poorly with health condition except at the extremes — both extremes. We hae diabetic people who are heavy and who are thin. We have people with athersclerosis who are heavy — and who are thin. We have people with high cholesterol and BMI around 22, people with normal cholesterol and BMI closer to 32.
    Third, BMI is often a measure of being fat but sometimes a measure of being muscular. I don’t know what studies exist of NFL players into their 70s; many of these were very large in their youth and early adulthood. Terry Bradshaw, at least, remains a husky man but I don’t know his muscle-fat composition.
    Declaring war on a symptom or condition that associates with health problems so loosely seems — well, actually, it seems bigoted to me. I happen to prefer slender body types but so what?

  2. The National Health Interview Survey is crap to start with. Unverified, self-reporting. Data “adjusted,” with unpublished algorithms, by people who have a stake in the outcome.

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