Exercise: More is More

Yesterday's post was all about absolute risk reduction vs relative risk reduction.  Last Friday, I commented on my Goldilock's theory of medicine with regards to IGF-1.  Well, as the author of this blog, I get to take writer's prerogative and contradict myself.  I don't intend to flail about like the wind - I just report what's available to me (and unfortunately, as I noted, I didn't learn enough statistics to convert relative into absolute risk reduction).

I mention this because a meta-analysis of 33 studies was published early online in Circulation yesterday linking exercise to heart disease.  No, this association isn't new.  I've written about the benefits of exercise many times in the past.  However, what's new is the quantitative nature of this link.

In other words, compared to those who do not engage in any exercise, achieving the minimum recommended 150min/wk of moderate intensity physical activity was associated with 14% relative reduction in heart disease.  The over-achievers who regularly engaged in 300min/wk of moderate intensity exercise received 20% relative risk reduction in heart disease.

Unfortunately, the law of diminishing returns (or marginal utility) came into play such that it took 5x minimum activity, eg 750min/wk of moderate intensity exercise in order to achieve 25% relative risk reduction in heart disease compared to those who didn't exercise at all.  But amazingly enough, even just 75min/wk or 10-15min/d was enough to achieve a small but statistically significant decrease in heart disease compared to absolute couch potatoes.

So it appears that when it comes to exercise, my Goldilock's theory doesn't apply.  Some exercise is better than none, but more is better.