Bo Nash is 38. He lives in Arlington, Texas, where he’s a technology director for a textbook publisher. He has a wife and child. And he’s 5’10” and 245 lbs – which means he is classed as obese.
In an effort to lose weight, Nash uses an app to record the calories he consumes and a Fitbit band to track the energy he expends. These tools bring an apparent precision: Nash can quantify the calories in each cracker crunched and stair climbed. But when it comes to weight gain, he finds that not all calories are equal. How much weight he gains or loses seems to depend less on the total number of calories, and more on where the calories come from and how he consumes them. The unit, he says, has a “nebulous quality to it”.