WIRED, All You Can Eat

In January of this year, the first subject checked into the metabolic ward at the National Institutes of Health in Bethesda, Maryland, to participate in one of the most rigorous dietary studies ever devised. For eight weeks, he was forbidden to leave. He spent two days of each week inside tiny airtight rooms known as metabolic chambers, where scientists determined precisely how many calories he was burning by measuring changes in oxygen and carbon dioxide in the air. He received meals through vacuum-sealed portholes so that the researchers’ breath wouldn’t interfere with their measurements. The food itself had been chemically analyzed to ensure an exact number of carbohydrate, protein, and fat calories.

The two-day stays in the chambers were only a small part of the testing, which was also being carried out on subjects at three other institutions around the US. Twice a month, the subjects were required to lie down for dual-energy x-ray absorpti­ometry scans, an accurate way to measure body fat. They offered up their veins again and again so that scientists could measure their lipids and hormone levels. They provided samples of their stools so the researchers could record the different colonies of bacteria residing in their guts…

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