Scientists are working to understand what hormonal and physiological cues in the body lead the brain to respond to food emotionally. iStockphoto.com hide caption

itoggle caption iStockphoto.com

As we age, our muscles deteriorate, and they don't repair as quickly as they used to. But the good news is that exercise and weightlifting can still make muscles stronger. Al Bello/Getty Images hide caption

itoggle caption Al Bello/Getty Images

Bob Karch is the chairman and a professor in the Department of Health and Fitness at American University. Here, he helps cross-country champion Steve Hallinan check his heart rate while cross-training on the bike. Allison Aubrey/NPR hide caption

itoggle caption Allison Aubrey/NPR

Budget Office Director Peter Orszag (far right) has found a way to turn walking into a competitive sport on Capitol Hill. Here, he walks through the Eisenhower Executive Office Building with Vice President Biden, President Obama and Treasury Secretary Timothy Geithner. Charles Dharapak/AP hide caption

itoggle caption Charles Dharapak/AP