Friday, June 1, 2012

Science Friday: Exercise is Bad for You?

Warning: As someone with both a family history of heart disease and a runner, my inherent bias is all over this post.

When someone says running will ruin your knees (it’s won't, it can actually be good for them), that marathons will kill you (an incredibly rare phenomenon), or some other argument that running is bad for you, the comeback is that it’s at least better than sitting on the couch snacking all day. But a new study says that 1 out of 10 times exercise may increase the levels of certain factors that may put you at risk for disease.

The group took results from six different published studies which looked at the effects of exercise. Some of the studies looked specifically at healthy people, others at obese or high-risk people, but the mean BMI of each cohort was in the overweight or obese range (which makes me wonder about those healthy groups.) The subjects exercised for 4-6 months and the mean VO2 max increased in each study (showing exercise was having an effect.) Each study measured four risk factors: 
Yes, this is definitely the healthier lifestyle.
1. Fasting insulin (high levels indicate insulin resistance which can lead to diabetes)
2. HDL (the "good" kind of cholesterol, which should go up with exercise)
3. Triglycerides (fat molecules; high levels are linked to heart disease and stroke)
4. Resting systolic blood pressure (high blood pressure is indicative of hypertension)
(Recently an article was published claiming HDL might not be as great a predictor of heart disease as once thought. We’ll have to wait and see if that holds up, but it would make the changes in HDL in this study less significant.) Using the data from these previous studies, this group looked at whether the subjects got better or worse regarding the risk factors. In each of the studies and for each of the four risk factors, about 10% of the subjects got worse.

Yikes, that gives sedentary people another excuse not to exercise, which I don’t think they need. Obviously this isn’t great for my argument that exercise is better than sitting on the couch. But let me still try to make it.

Let's turn this around: we take 10 people at risk or overweight and get them to exercise. Nine of them improve (or stay the same) on measures we think have something to do with disease risk. One of them doesn’t. That seems like good odds to me. Furthermore, it doesn’t mean the one gets heart disease, just that the risk factors doctors associate with disease go in the wrong direction. But if the new HDL study holds up to more research, we might be barking up the wrong tree with these risk factors. It’s important to note the study doesn't actually look at disease or deaths from disease. Other studies (summary here) have done that, and exercise overwhelmingly helps. Finally, there is always variability. Just like some drugs don't work on everyone, exercise might not either.

I am curious to know if after more time exercising the relationship changes. It’s a whirlwind of soreness, pain, and changes to your body when you first start to get in shape. And despite what some people making excuses think, it does get better. I wonder if we follow these people for longer if that might be the case for these risk factors as well.

Like I said, this will make it harder to argue with the couch potatoes. But regardless, I don't exercise purely to help my heart. There are many other benefits, so I'll keep arguing and I'll keep running.

Other (semi-related) news this week: NYC is looking to ban large sugary drinks. This means any drinks over 16 fl oz. (which includes most drinks since America has redefined what "large" means.) I think this idea is superb. Even better, it doesn't include milkshakes.  

Dream big, 
Teal

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