Obese people -- those with a BMI of 30 to 34.9 -- have a 44 percent higher risk of death from any cause compared with those in the most-favorable range, according to a study in the New England Journal of Medicine. iStockphoto.com hide caption

itoggle caption iStockphoto.com

Our brains have chemical pathways that make us feel good when we eat, and really good when we eat sweet or fatty foods with high calories. Scientists see these same chemical pathways used in cases of drug addiction. Paul Ellis/AFP/Getty Images hide caption

itoggle caption Paul Ellis/AFP/Getty Images

Experts say it's nearly impossible to address U.S. fiscal problems without coming to terms with Medicare. The program provides coverage to 47 million Americans, consumes 12 percent of the federal budget and accounts for $1 of every $5 spent on health care each year. Its future includes 78 million baby boomers. Kirby Hamilton/iStockphoto.com hide caption

itoggle caption Kirby Hamilton/iStockphoto.com

Cornfields in Malawi, like this one, can be used to grow legumes such as pigeon peas, which replenish the soil and are more nutritious than corn. Michelly Rall/Getty Images hide caption

itoggle caption Michelly Rall/Getty Images

Mexico's President Felipe Calderon (left) starts a wind turbine that will help power the United Nations Climate Change Conference in Cancun. Officials will spend the next two weeks debating how to mobilize money to cope with climate change as temperatures climb, ice melts and seas rise. Israel Leal/AP hide caption

itoggle caption Israel Leal/AP

The deep-water-research submarine Alvin is launched from Atlantis. Scientists are studying how ecosystems in the Gulf of Mexico may have been affected by the Deepwater Horizon oil spill. Richard Harris/NPR hide caption

itoggle caption Richard Harris/NPR

Megan Lindsey (right) and her friend Alexandria Bodfish at soccer camp at University of Notre Dame.  Megan, 14, suffered concussions twice this fall while playing soccer. Courtesy of Barbara Wirtz hide caption

itoggle caption Courtesy of Barbara Wirtz

Cycling has at least tripled over the past two decades in several big cities across the U.S., including Minneapolis, Chicago and San Francisco. Jonathan Steinberg hide caption

itoggle caption Jonathan Steinberg