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Scientists are using reality TV to crack the mysteries of the human body — specifically, why people tend to gain so much weight back after major weight losses. Following contestants from NBC's The Biggest Loser, researchers concluded that it is because bodies biologically fight tooth-and-nail to climb back to their original weight.

The problem mainly lies with metabolisms, which slow radically as the body loses weight so that they eventually don't burn enough calories to maintain the thinner body size. Former contestant Danny Cahill, 46, for example, weighed 430 pounds before The Biggest Loser, 191 at the finale of the show, and six years later now weighs 295 pounds. His body burns 800 fewer calories a day than would be expected for a man of his size.

"All my friends were drinking beer and not gaining massive amounts of weight. The moment I started drinking beer, there goes another 20 pounds. I said, 'This is not right. Something is wrong with my body,''' Cahill said.

It turns out, he's right. "This is a subset of the most successful [dieters]," Dr. David Ludwig, who was not involved in the study, said of the Biggest Loser findings. "If they don't show a return to normal in metabolism, what hope is there for the rest of us?"

But with the problem identified, Ludwig adds researchers and people concerned about their weight shouldn't lose hope. "[It] shouldn't be interpreted to mean we are doomed to battle our biology or remain fat," Ludwig said. "It means we need to explore other approaches."

Learn more about what those approaches might be, and the science behind weight gain and loss, at The New York Times.