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Two-thirds of Americans are overweight. And when many of them try to take off the extra pounds, their bodies fight to stay fat. Tara Parker-Pope, who described "The Fat Trap" in The New York Times Magazine, and Dr. Arthur Frank talk about why some people appear more biologically prone to obesity.

When Facebook engineer Arturo Bejar observed users were reporting pictures of themselves, not those with illegal content, he recognized the need for a better way for users to resolve internal conflicts. Bejar talks about how Facebook is trying to encourage compassion in online social interaction.

NPR's Neal Conan reads from Talk of the Nation listener comments on previous show topics, including our annual show remembering remarkable lives lost, and a recent proposal to change the laws governing what work children may do on farms.

A major medical group issued ethical guidelines on Monday that take the provocative position of urging doctors to consider cost-effectiveness when deciding how to treat their patients.

The American College of Physicians, the second-largest U.S. doctors' group after the American Medical Association, included the recommendation in the latest version of its ethics manual, which provides guidance for some 132,000 internists nationwide.

We knew defense cuts were coming, but The New York Times is reporting that Defense Secretary Leon Panetta will unveil $450 billion in cuts this week. With the announcement reports the Times, will also come a new philosophy for the Pentagon.

The Times reports:

Most everyone's spirits are a bit deflated after the holidays. So, as a literary antidote, I recommend a just-published anthology called New York Diaries: 1609 – 2009. Editor Teresa Carpenter has collected four centuries worth of diary excerpts written by people, great and small, who've lived in or just passed through one of the greatest cities in the world.

Iran issued a threat to a U.S. aircraft carier, today, which further complicates the tense relationship between the two countries. The threat comes just a day after Iran performed naval maneuvers in the Strait of Hormuz.

In yet another sign that the economy is limping forward, the Commerce Department said today that spending on construction rose 1.2 percent in November for the third time in four months.