June 2012

Of the carbohydrate obesity thesis? Check out Stephen Guyenet’s lastest post about a new study that finds that sugar has to be palatable to be fattening in mice.  In other words, despite an increase in calories from sugarwater, mice whose sugar receptor taste buds had been knocked out did not gain weight like normal mice.

Whatever conclusions different people might draw from this study, I think it goes to show that, however fat gain and loss works, it is just a heckuva lot more complicated than the carbohydrate-insulin obesity thesis most recently popularized by Gary Taubes.

For my part, I’ve added roughly six pounds of potatoes per week back into my diet over the last nine months and haven’t gained an ounce. Not saying a low-carb approach to Paleo isn’t right for some, just that the whole “safe starch” thing is working really well for me and I feel great.

It’s easy to get too obsessed and mechanistic in our thinking about the extent to which we can control our health by controlling our diet. If the crazy stuff coming out the field of epigenetics suggests anything, it is that health is about a rich array of dietary and lifestyle factors that all interact with each other in complex ways.

To me, it makes the whole macronutrient debate look pretty silly. And as the New York Times has reported, it’s not about the numbers alone. It’s about the total lifestyle that went into producing the numbers.

In the long run, once you’re eating a relatively clean diet, variants on that just pale in comparison to things like stress levels, time outdoors, sleep, community, etc. In other words, many of the aspects of the lives of traditional/paleo peoples that are so hard to replicate in the modern world. Perhaps given that difficulty, focus on the one thing we can control most easily–diet–is understandable.

I’ve posted before about studies suggesting that excessive endurance exercise is not good for your heart and health.

Here’s another study suggesting that marathons, iron man distance triathlons, and very long distance bicycle races do more good than harm. They may cause structural changes to the heart and large arteries. Over time, this can lead to scarring on your heart, among other things. Of course, the study includes a pretty big caveat:

However, this concept is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity. Notwithstanding, the hypothesis that long-term excessive endurance exercise may induce adverse CV remodeling warrants further investigation to identify at-risk individuals and formulate physical fitness regimens for conferring optimal CV health and longevity.

I think the bottom line from this and other studies like it is that is that ultra-endurance stuff just isn’t good for you. Of course, endurance people generally aren’t doing it because they think it makes them healthy. They are doing it because they enjoy the challenge, and because it becomes a sort of drug.  It makes you fit, but it doesn’t make you healthy. On that note, this and other studies suggest that the main health benefits of cardio exercise accrue at 30-60 minutes per day. After that, you’ve reached the point of diminishing returns.

I’m currently cycling an average of 8 hours per week, according to Strava.  More than I need for health, for sure, but not as much as I would like all the same. It’s easy when it’s not exercise to you.  I mean, it never really occurred to me that I might bike for health alone. I do it for the fun and the time outdoors. I’m still trying to mix it up more than I used to with walking, hiking, and weights. I may even do something crazy like enter the Julian Death March race this October, which certainly enters into ultra-endurance territory. One big challenge a year?  Might be a good way to set the bar at a sane level.