Monday, June 17, 2013

Why I’m skinny

I weigh about the same today as I did in college: 160 pounds. In my entire life I’ve never weighed more than 170. Maintaining my weight has been effortless: I eat pretty much whatever I like, whenever I want, and in whatever quantity suits me at the time.  I know, I know, this is not normal and I should be thankful.  The vast majority of people, especially past middle age, seem like they have to starve themselves to keep from piling on the pounds.

Why?  I’m not particularly athletic. Although I don’t think of myself as sedentary per se, I’m hardly the type who does regular biking or jogging.

It might be genetic, but it’s hard to say.  My 23andme results suggest, if anything, I have the opposite problem (72/100 vs 64/100 for people like me).  On the other hand, I have the GG marker for rs925946, which puts me at lower odds, but who knows.  Most of my relatives are on the thin side, but we have our share of porkers too. I doubt my DNA explains everything.

One of my favorite theories is that I’m host to a benevolent microbiome, a colony of bacteria in my digestive system that processes food as I eat it, to prevent me from becoming either too skinny or too fat. But I’ve been hospitalized with some powerful antibiotics that probably killed off whatever beneficial bacteria I have, so that’s not persuasive either.

That leaves the most obvious possibility – that I just don’t eat enough – but I’ve never proven that objectively. Until now.

For the past week I’ve been wearing the BodyMedia Fit, a $90 simple and non-obtrusive armband that’s so light it’s easy to forget I have it on. Using four hi-tech sensors, it calculates my metabolism with 92% accuracy compared to the Gold Standard lab equipment. To track my food intake, I use MyFitnessPal, a (free) iPhone app with a huge database of food types (and super-handy UPC code scanner) that makes it easy to enter what I ate each day.

Here are the results:


The bottom line is that I’m thin because I don’t overeat. Apparently my metabolism is set to burn off whatever comes in, which turns out to be well within the range of what it takes to stay thin.

I’m not a weight loss expert, and this is not a testimonial for how to lose weight. Everyone is different, and my results probably won’t help you. But if you want to understand what your body is doing – the first step toward making any changes – then I highly recommend getting a device like this one to understand your metabolism objectively.

Incidentally, a good follow-up question is why I don’t feel hungry. I don’t think weight issues can be solved with self-control: diets fail in the long run if they depend on willpower. Seth Roberts always has thoughts about this that intrigue me and I’ll spend more time thinking about that in the future.

[Placeholder: I’m writing up many more details, including the raw data, about my week with BodyMedia and I’ll post a link here when I’m finished]