TWEETORIAL AHEAD: This summer, I had a rare opportunity to join an @NIH study and spend 23 hours sealed inside an 11-by-11.5-foot metabolic chamber... and I got a granular look at how metabolism works. A few takeaways: 1) *Metabolism is not a single thing in you that you can control.* It's thousands of chemical reactions that turn the energy (calories) we eat and drink into fuel in every cell. These reactions change in response to our environments & behaviors, in ways we have little control.