Tag Archives: health

Is BMI Worse Than Worthless?

The statistical gurus at FiveThirtyEight have looked at the ubiquitous body mass index (BMI) and come to a conclusion that many of us suspected: it stinks as a measure of health. In fact I’d argue that it might be worse than useless, in fact might even be harmful, because it misleads people into thinking they are not at risk of negative health effects because they have a BMI in the “normal” range.

Taken alone as an indicator of health, the BMI is misleading. A study by researchers at UCLA published this month in the International Journal of Obesity looked at 40,420 adults in the most recent U.S. National Health and Nutrition Examination Survey and assessed their health as measured by six accepted metrics, including blood pressure, cholesterol and C-reactive protein (a gauge of inflammation). It found that 47 percent of people classified as overweight by BMI and 29 percent of those who qualified as obese were healthy as measured by at least five of those other metrics. Meanwhile, 31 percent of normal-weight people were unhealthy by two or more of the same measures.2 Using BMI alone as a measure of health would misclassify almost 75 million adults in the U.S., the authors concluded…

The researchers analyzed the health data for 15,184 adults who were part of the National Health and Nutrition Examination Survey. Their results,published in the Annals of Internal Medicine, were pretty surprising: They showed that midsection obesity was a killer, even among people with normal BMIs. For example, a man with a BMI of 22 (putting him firmly in the normal range) but too much belly fat according to his waist-to-hip ratio had an 87 percent higher mortality risk than a guy with the same BMI and a healthy waist-to-hip ratio.

What’s more, a man with a normal BMI and disproportionately big belly had more than twice the mortality risk of a man who was overweight or obese by BMI but not by waistline. Among women, those who were normal weight by BMI but had a high waist-to-hip ratio had a 48 percent higher mortality risk than those with a similar BMI but a healthy waist-to-hip ratio, and a 32 percent higher risk compared with those who were obese according to BMI only.

This is the kind of thing that leads me to think BMI has more in common with phrenology than mainstream health care practices.

Caveat Lector

The next time you read, see or hear a news story related to dietary or health study claims you might want to keep remember story titled “I Fooled Millions Into Thinking Chocolate Helps Weight Loss. Here’s How” 

“Slim by Chocolate!” the headlines blared. A team of German researchers had found that people on a low-carb diet lost weight 10 percent faster if they ate a chocolate bar every day. It made the front page of Bild, Europe’s largest daily newspaper, just beneath their update about the Germanwings crash. From there, it ricocheted around the internet and beyond, making news in more than 20 countries and half a dozen languages. It was discussed on television news shows. It appeared in glossy print, most recently in the June issue of Shape magazine (“Why You Must Eat Chocolate Daily,” page 128). Not only does chocolate accelerate weight loss, the study found, but it leads to healthier cholesterol levels and overall increased well-being. The Bild story quotes the study’s lead author, Johannes Bohannon, Ph.D., research director of the Institute of Diet and Health: “The best part is you can buy chocolate everywhere.”

I am Johannes Bohannon, Ph.D. Well, actually my name is John, and I’m a journalist. I do have a Ph.D., but it’s in the molecular biology of bacteria, not humans. The Institute of Diet and Health? That’s nothing more than a website.

Other than those fibs, the study was 100 percent authentic. My colleagues and I recruited actual human subjects in Germany. We ran an actual clinical trial, with subjects randomly assigned to different diet regimes. And the statistically significant benefits of chocolate that we reported are based on the actual data. It was, in fact, a fairly typical study for the field of diet research. Which is to say: It was terrible science. The results are meaningless, and the health claims that the media blasted out to millions of people around the world are utterly unfounded.

Here’s how we did it.

You really should read the whole thing to see exactly how easy it is to game the science journalism field. And if you want to be happy you should also embrace the strategy of believing the studies that purport to show the health benefits of eating/drinking whatever you want and ignoring those that claim those same habits are unhealthy.

Works for me.

Fighting Anecdotal Fire With Anecdotal Fire

This article in Slate, written by a woman whose mother did not have her vaccinated and thus suffered through mumps, measles, rubella, etc., is an excellent piece of thinking about the current hubbub related to vaccinations. I like this part in particular:

I find myself wondering about the claim that complications from childhood illnesses are extremely rare but that “vaccine injuries” are rampant. If this is the case, I struggle to understand why I know far more people who have experienced complications from preventable childhood illnesses than I have ever met with complications from vaccines. I have friends who became deaf from measles. I have a partially sighted friend who contracted rubella in the womb. My ex got pneumonia from chickenpox. A friend’s brother died from meningitis. 

Anecdotal evidence is nothing to base decisions on. But when facts and evidence-based science aren’t good enough to sway someone’s opinion about vaccinations, then this is where I come from. After all, anecdotes are the anti-vaccine supporters’ way: “This is my personal experience.” Well, my personal experience prompts me to vaccinate my children and myself. I got the flu vaccine recently, and I got the whooping cough booster to protect my son in the womb. My natural immunity—from having whooping cough at age 5—would not have protected him once he was born.

(Bold emphasis mine)

There are a lot of things that frustrate me about the vaccination debate, not the least of which is that someone else’s decision to ignore science and logic might adversely affect other peoples’ health, but what really gets my goat is the trend the author points out of people refuting evidence with anecdote.

Recently I saw a post on Facebook in which someone shared an information piece of dubious origin that said something like: “Number of deaths from measles last year: 0. Number of deaths from measles vaccines: 106” There are so many things wrong with this, but here are the most obvious:

  • First of all, if you’re going to share this kind of data then please share the source so it can be verified as legitimate.
  • Second, if it is legitimate then please share whether or not that’s in the US or the world. Why? Because if it’s the world then I can flat out tell you it’s BS. From the World Health Org.:
    WHO warned today that progress towards the elimination of measles has stalled. The number of deaths from measles increased from an estimated 122 000 in 2012 to 145 700 in 2013, according to new data published in the WHO Weekly Epidemiological Report and the Centers for Disease Control and Prevention’s (CDC) Morbidity and Mortality Weekly Report. The estimated number of measles deaths in 2013 represents a 75% decline in mortality since 2000, significantly below the target of a 95% reduction in deaths between 2000 and 2015.
  • Third, if it IS true and it is just the US then use percentages rather than raw numbers. One reason so few people would have died from measles is because so many people were vaccinated! What percentage of people who got the vaccine died? Vanishingly small. And while the percentage of people who die after contracting measles would also be vanishingly small, that doesn’t mean the disease doesn’t wreak havoc by making people very sick.

So here’s the point, and I’m going to type it really slowly so the anti-vaxxers can keep up: You are entitled to your opinion. You are also entitled to ignore science and generally do stupid things. Your entitlement ends where others’ well being begins, thus if you decide to not vaccinate your children then your family should NOT be allowed to partake in any public activities or enjoy any other societal benefits that would put you in direct contact with the vaccinated population. No schools, no restaurants, no stores, no swimming pools, no movie theaters, no malls, no amusement parks, no public parks and no places of business (okay, maybe Walmart). Nada. Nothing. Don’t want to participate in 21st century public health programs? Fine, then don’t participate in 21st century public gatherings.

Poorly Educated Poor White Women Dying Young

From a story in The American Prospect:

Everything about Crystal’s life was ordinary, except for her death. She is one of a demographic—white women who don’t graduate from high school—whose life expectancy has declined dramatically over the past 18 years. These women can now expect to die five years earlier than the generation before them. It is an unheard-of drop for a wealthy country in the age of modern medicine. Throughout history, technological and scientific innovation have put death off longer and longer, but the benefits of those advances have not been shared equally, especially across the race and class divides that characterize 21st–century America. Lack of access to education, medical care, good wages, and healthy food isn’t just leaving the worst-off Americans behind. It’s killing them.

The journal Health Affairs reported the five-year drop in August. The article’s lead author, Jay Olshansky, who studies human longevity at the University of Illinois at Chicago, with a team of researchers looked at death rates for different groups from 1990 to 2008. White men without high-school diplomas had lost three years of life expectancy, but it was the decline for women like Crystal that made the study news. Previous studies had shown that the least-educated whites began dying younger in the 2000s, but only by about a year. Olshansky and his colleagues did something the other studies hadn’t: They isolated high-school dropouts and measured their outcomes instead of lumping them in with high-school graduates who did not go to college.

The last time researchers found a change of this magnitude, Russian men had lost seven years after the fall of the Soviet Union, when they began drinking more and taking on other risky behaviors. Although women generally outlive men in the U.S., such a large decline in the average age of death, from almost 79 to a little more than 73, suggests that an increasing number of women are dying in their twenties, thirties, and forties. “We actually don’t know the exact reasons why it’s happened,” Olshansky says. “I wish we did.”…

Researchers have long known that high-school dropouts like Crystal are unlikely to live as long as people who have gone to college. But why would they be slipping behind the generation before them? James Jackson, a public-health researcher at the University of Michigan, believes it’s because life became more difficult for the least-educated in the 1990s and 2000s. Broad-scale shifts in society increasingly isolate those who don’t finish high school from good jobs, marriageable partners, and healthier communities. “Hope is lowered. If you drop out of school, say, in the last 20 years or so, you just had less hope for ever making it and being anything,” Jackson says. “The opportunities available to you are very different than what they were 20 or 30 years ago. What kind of job are you going to get if you drop out at 16? No job.”

If you were to poll folks here in the Piedmont of North Carolina you would find a lot of people who agree with this premise. We're in the midst of a tectonic shift from a manufacturing-based economy to a knowledge-based economy and there are a lot of people who once made a good living with their high school (or less) education who are now struggling to keep their heads above water. Scary, scary stuff.


Don’t Just Sit There

Just so you know, sitting too much is bad for you.

The above definition may seem rather intuitive, but this is not the way that the term sedentary has been used by exercise science researchers for the past 50 years. Up until very recently, referring to someone as sedentary meant simply that they were not meeting current guidelines for physical activity. In simple terms, if you were exercising for 60+ minutes/day, you were considered physically active. If you were exercising 10 minutes/day, you were sedentary. Case closed. But as we will discuss below, sedentary time is closely associated with health risk regardless of how much physical activity you perform on a daily basis. Further, it is entirely possible to meet current physical activity guidelines while still being incredibly sedentary. Thus, to quote researcher Marc Hamilton, sitting too much is not the same as exercising too little. (if you take only one thing from this post, let it be that quote from Dr Hamilton). Which is why it is so important that when we use the term "sedentary", we are all on the same page about what that means…

 But what is fascinating is that the relationship between sitting time and mortality was independent of physical activity levels. In fact, individuals who sat the most were roughly 50% more likely to die during the follow-up period than individuals who sat the least, even after controlling for age, smoking, and physical activity levels. Further analyses suggested that the relationship between sitting time and mortality was also independent of body weight. This suggests that all things being equal (body weight, physical activity levels, smoking, alcohol intake, age, and sex) the person who sits more is at a higher risk of death than the person who sits less.

I'm screwed.