It's 9:25 in the morning, and I'm lying on a twin bed at the Pennington Biomedical Research Center, one of the country's premier facilities for the study of body weight and metabolism. My room here on the outskirts of Baton Rouge boasts all the amenities of a nicely outfitted, minimum-security prison cell. Besides the bed, I have a toilet, sink, cable TV, DVD player, computer, treadmill, even a minifridge.
The latter, alas, is for storing urine samples only. Best not to forget and reach for a Mountain Dew.
Everything I can consume over the next 24 hours of voluntary incarceration is under the tight control of PBRC staff nutritionists. At established intervals, nurses will pass me premeasured portions of a "standard American diet" (15 percent protein, 50 percent carbohydrates, 35 percent fat) through a special air-locking slot in the wall.
Though I've come to think of this as my Hannibal Lecter slot, it serves a necessary scientific function: preventing atmospheric contamination of the 27,000 liters of air surrounding me. This sea of air, like my calorie intake, is under scrupulous regulation. An inflow pipe on the floor continuously pumps in exactly 60 liters of fresh air per minute — untainted by contact with any human lungs, mine included. At the same time, 22 evenly spaced outflow holes in the ceiling siphon off my "breathed" samples for detailed analysis.
"The official name of the room you're now in is a 'whole-body indirect calorimeter,' " explains PBRC biomedical engineer Tuong Nguyen, over an intercom from an adjacent lab. As he begins to deliver Calorimetry for Dummies, he simultaneously monitors me with a video camera that has infrared capability for nighttime observations. "The reason we call it indirect calorimetry is because we're not measuring your caloric burn directly. Instead, we're detecting how much oxygen your body is using at any given point, and how much carbon dioxide you're giving off."
Complicated physiological formulae, Nguyen adds, will then convert my gleaned gaseous data into a minute-by-minute count of every calorie I burn during sleep, work, meals, exercise, rest, TV viewing, and so forth. Other formulae will take the constantly shifting ratio of my oxygen use and carbon dioxide production to reveal what proportions of these calories are coming from fat and carbohydrate burning, respectively. (Note: When our bodies use protein for fuel, it's converted to carbohydrate first.)
At this point, Nguyen stops explicating and encourages me to begin resting in earnest. The steady whoosh of circulating air all but drowns out the gurgles of my gut, which has not seen food in the past 14 hours. Before I know it, my mind wanders to the octopus of air tubes hidden in the ceiling. I imagine my slow, relaxed puffs of exhaled gas wending their way through a drying agent before being measured by incredibly fine-tuned sensors.
"Okay," says Nguyen, "you can get up now and move around. Breakfast will be ready in a couple of minutes."
It's hard to believe a whole hour has passed.
Before I rise, I find the remote and turn on the TV. A white-trash woman in a black bikini is yelling obscenities on Jerry Springer. I can see her cellulite jodhpurs jiggling in rage. She has to be burning serious calories here, I think — though probably not, it would appear, the ones in her thighs.
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