\u201cFor me, a calorie is a unit of measurement that\u2019s a real pain in the rear.\u201d<\/p>\n
Bo Nash is 38. He lives in Arlington, Texas, where he\u2019s a technology director for a textbook publisher. And he\u2019s 5\u201910\u201d and 245 lbs \u2013 which means he is classed as obese.<\/p>\n
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 \u201cnebulous quality to it\u201d.<\/p>\n
Tara Haelle is also obese. She had her second son on St Patrick\u2019s Day in 2014, and hasn\u2019t been able to lose the 70 lbs she gained during pregnancy. Haelle is a freelance science journalist, based in Illinois. She understands the science of weight loss, but, like Nash, doesn\u2019t see it translate into practice. \u201cIt makes sense from a mathematical and scientific and even visceral level that what you put in and what you take out, measured in the discrete unit of the calorie, should balance,\u201d says Haelle. \u201cBut it doesn\u2019t seem to work that way.\u201d<\/p>\n
Nash and Haelle are in good company: more than two-thirds of American adults are overweight or obese. For many of them, the cure is diet: one in three are attempting to lose weight in this way at any given moment. Yet there is ample evidence that diets rarely lead to sustained weight loss. These are expensive failures. This inability to curb the extraordinary prevalence of obesity costs the United States more than $147 billion in healthcare, as well as $4.3 billion in job absenteeism and yet more in lost productivity.<\/p>\n
At the heart of this issue is a single unit of measurement \u2013 the calorie \u2013 and some seemingly straightforward arithmetic. \u201cTo lose weight, you must use up more calories than you take in,\u201d according to the Centers for Disease Control and Prevention. Dieters like Nash and Haelle could eat all their meals at McDonald\u2019s and still lose weight, provided they burn enough calories, says Marion Nestle, professor of nutrition, food studies and public health at New York University. \u201cReally, that\u2019s all it takes.\u201d<\/p>\n
But Nash and Haelle do not find weight control so simple. And part of the problem goes way beyond individual self-control. The numbers logged in Nash\u2019s Fitbit, or printed on the food labels that Haelle reads religiously, are at best good guesses. Worse yet, as scientists are increasingly finding, some of those calorie counts are flat-out wrong \u2013 off by more than enough, for instance, to wipe out the calories Haelle burns by running an extra mile on a treadmill. A calorie isn\u2019t just a calorie. And our mistaken faith in the power of this seemingly simple measurement may be hindering the fight against obesity.<\/p>\n