Friday, November 16, 2012

Science Friday: Days to Your Life

I don’t run to add days to my life, I run to add life to my days.

That quote is catchy and memorable because the first part is expected; we know that running and being active makes you live longer. The point of the quote is that it goes beyond that.

But today let’s focus on that first part. How many days are we talking about, really? Research recently published in PLOS Medicine attempted to quantify that number. The authors pooled findings from a couple of large studies (such as the Women’s Health Study and the NIH-AARP Diet and Health Study) and accumulated data on close to 650,000 people. The studies included reports from a ten-year follow up and so the authors were able to correlate amounts of exercise with how long people lived. A quick perspective to understand the numbers on the graph below: physical activity was quantified as metabolic equivalents (METs); 7.5 MET-hr/wk is roughly equal to 150 minutes of brisk walking per week, or 75 minutes of vigorous activity (such as running.) 7.5 MET-hr/wk is about the recommendation doctors and public health advocates encourage for a healthy lifestyle.

In the graph, you can see that as "leisure time physical activity" (i.e. exercising in your free time, such as running or walking) increases, years of life increase as well. As you can tell from the sharp increase to the left of the graph, just getting off the couch for an hour or so each week helps a lot. (Activities such as brisk walking for 75 minutes/week increased life expectancy by 1.8 years.) People getting the recommended amount of exercise (150 minutes of walking or 75 minutes of running) increase their life expectancy by 3.4 years. Incredibly, although the effect lessens, it keeps going up with more activity. (No, marathoning likely won't kill you.)

The study goes on to talk about the relationship between BMI, physical activity, and longevity. This is the relatively new concept of being “fit and fat.” Annoyingly, some people can’t seem to lose weight despite a rigorous and routine exercise program. Are these people better off health wise than those much hated skinny people who never have to exercise? So far, the research says yes: even if you don’t lose weight, exercise has other (perhaps less superficially obvious) benefits to your health. So fit and fat people are better off than those inactive, normal weight people (the lean and lazy? skinny and slacking? slim and slothful?)

This study provides more evidence. Overweight people (BMI between 25 and 29.9) who were active lived 4.7 years longer than inactive, normal weight people (BMI between 18 and 24.9.) Even active obese people (BMI between 30-34.9) lived 3.1 years longer than those lean and lazy people. However, this effect disappeared when people had BMIs greater than 35 (severely obese category.) It seems that at that point, the health risks of being overweight outweigh (no pun intended!) the benefits of working out.

In summary, it tells us what we already knew: running can add days to our lives. Now we know just how many: approximately 1,241 (3.4 years) for 75 minutes of running per week. But the life added to our days? That’s harder to quantify.

Dream big,

1 comment :

  1. Good stuff, it's nice to see an idea that is broadly supported quantified!