Walking more - and measuring it

Here's a new, smaller entry in my self-quantifiers series. Alexis Madrigal, in The Atlantic, has posted a column about his new fitness program: walking. Yes, walking, that famous 10,000 steps per day to fitness, or at least health. According to Madrigal, that's about double the American number of just over 5000 steps per day.

So, how much do you have to walk every day to get up to those 10,000 steps? Ten thousand steps is about five miles (the distance varies with your height and the length of your stride). You don't have to set out to walk five miles to get that number of steps in. But you do have to make an effort to walk places that you might otherwise drive to. In New York City, that's not a problem, but in other places, where there are no sidewalks, it can be.

Madrigal puts it like this:

Americans lag behind the rest of the world in steps taken precisely because we travel so rarely for transportation's sake. Our cities are spread out (NYC excepted) and car culture is everywhere. A Centers for Disease Control study found that almost 40 percent of Americans had not walked for 10 straight minutes in the past week!

Even more interestingly, Gregg Furie of Yale Medical School led a study that showed that less than 25 percent or people walked or biked as a means to get from one place to another for more than 10 straight minutes in a given week. And yet, Furie's study found that people who engaged in "active transportation," as he calls it, had lower BMI, smaller waists, and lower odds of hypertension and diabetes.

I'll give him the last word: "when you have the opportunity to walk as a means to an end, take it."
 

Obesity studies

You may have read yesterday about a study published in the Journal of the American Medical Association concluding that, although obesity overall was associated with higher mortality rates, overweight (identified by Body Mass Index, or BMI) was associated with statistically significant lower mortality rates. This conclusion has been trumpeted as vindication for the view that we are, perhaps, overfocused on the importance of weight loss for good health. See, for example, here, here, and here.

This conclusion depends, of course, on BMI being a good proxy for mortality risk. There's some evidence that it's not. One drawback, according to Well-Being Wire, is that BMI fails to account for an individual's exercise habits - you can be fit but fit with a high BMI, and slender but sedentary with a low BMI. In those cases, BMI won't tell you who is healthier.

In any case, the study is not an endorsement of heaviness or weight gain. The authors conclude: 

Relative to normal weight, obesity (all grades) and grades 2 and 3 obesity were both associated with significantly higher all-cause mortality. Grade 1 obesity was not associated with higher mortality, suggesting that the excess mortality in obesity may predominantly be due to elevated mortality at higher BMI levels.

And even the next sentence, "Overweight was associated with significantly lower all-cause mortality," needs to be read with some skepticism. As Lindsay Abrams writes at TheAtlantic's web site:

the study fails to take into account any of the various other measures used to assess health. It ignores blood pressure, blood sugar, and cholesterol -- high levels of all are directly associated with a variety of chronic conditions and diseases -- not to mention mental health and life satisfaction scores.  

She provides some interesting pictures that make the point about BMI, and concludes:

While in the most basic of ways, it makes sense to pay attention to the number on the scale, it only gives us one metric of health that, if not understood in context, is basically useless. If we could get used to looking at weight more holistically, in terms of overall health, the link between BMI and longevity wouldn't be so shocking.

So read the study. Think about it. And then continue to work out.