I recently read an article discussing ethnic differences in insulin sensitivity in relation to obesity. The conclusion was that formerly overweight African American women were more insulin sensitive than never-overweight African American women, and that insulin-sensitive African American women were more likely to gain weight than the insulin-resistant women.
In other words, the suggestion was that contrary to the concept that insulin resistance contributes to obesity, these researchers found that insulin resistance protected against obesity, at least in African American women.
However, that’s not what I want to discuss here, because the study was limited to African American women and might not apply in general.
In this study, they measured a lot of things, including activity levels. What I want to discuss is their definition of sedentary: "less than or equal to 1 day/week structured exercise."
Come again? Exercise has to be "structured" in order to count as exercise?
Imagine you’re a postal worker whose job involves old-fashioned delivery of letters by hand. True, todays postal workers no longer carry heavy sacks of mail. They wheel the bags around. But they’re still walking.
Now imagine that you come home after 7 or 8 hours standing on your feet sorting mail and then going out and walking from house to house to deliver it. Do you think you’d feel like structured exercise on a treadmill?
I think not.
But do I think you’d be considered sedentary?
I do not.
This is one problem with this sort of study. Definitions of various terms can differ from study to study. And they can be misleading. Let’s say some other study used the same definition of sedentary and showed that sedentary people had X or Y problem. But if lots of those people were like the postal workers, the results would be misleading.
Definitions of diets are often misleading. One often sees a headline that reports that mice on a "high-fat diet" have this problem and that problem. What the stories don’t mention is that the high-fat mouse diet was also high in carbohydrate. So patients on low-carb, high-fat diets are chastised by their doctors or dieticians, who saw the titles of the mouse studies and didn’t read or analyze the whole papers.
The moral is, Buyer Beware. We’re all "buying" health advice from many sources, and we need to double-check to make sure that the advice we get is valid.