We are all Russian nesting dolls: Our intestines house many bacteria, which house many viruses. These so-called bacteriophages are likely as important for our health as the bacteria they live in. Lisa Brown for NPR hide caption

itoggle caption Lisa Brown for NPR

Helping employees take the time to go for a walk instead of reaching for junk food when energy flags boosts productivity, some firms find. Jamie Grill Photography/Tetra Images/Corbis hide caption

itoggle caption Jamie Grill Photography/Tetra Images/Corbis

Euclid Market, a corner store in East Los Angeles, recently got a makeover to promote healthier eating. It not only sells more fruits and vegetables, but also offers cooking classes and nutrition education. Courtesy of Margaret Molloy/UCLA Fielding School of Public Health hide caption

itoggle caption Courtesy of Margaret Molloy/UCLA Fielding School of Public Health

Researchers say that setting your thermostat a little lower can help you burn more calories. iStockphoto hide caption

itoggle caption iStockphoto

Kendall Schrantz, center, stretches after a class at Downsize Fitness in Fort Worth. Lauren Silverman for NPR hide caption

itoggle caption Lauren Silverman for NPR

Americans are dining out less and eating at home more, new government research shows. This may mean more family dinners, like this one at the Brown-Spencer home in Mechanicsville, Va. Maggie Starbard/NPR hide caption

itoggle caption Maggie Starbard/NPR

The U.K. has plenty of fresh produce available, such as these vegetables on display at a garden show in Southport, England. But these healthy options cost more in the U.K. than in any other country in Western Europe. Christopher Furlong/Getty Images hide caption

itoggle caption Christopher Furlong/Getty Images

To make a more healthful version of Edy's Grand Ice Cream, Nestle developed a technology that could cut half the fat and two-thirds of the calories from the frozen treat. Erik S. Lesser/Getty Images hide caption

itoggle caption Erik S. Lesser/Getty Images

Gym members warm up on treadmills at Downsize Fitness in Addison, Texas. Membership at the gym is limited to people who have a high body mass index. LM Otero/AP hide caption

itoggle caption LM Otero/AP