August 2, 2013 9:40 am Body Obsession Swells on Social Media Experts are warning parents about the danger of a new trend that’s sweeping the Internet, called “The Thigh Gap,” an obsession for teen girls who want thin legs. US & World Videos 1:43 Traces of bird flu virus found in 1 in 5 samples of pasteurized milk, FDA says 2:42 Mother, surrogate celebrate a perfect ending to their long journey 1:12 Watch: Why vaccines are contributing to improved public health 1:53 The Helix School in San Rafael growing with the community 3:33 Bay Area sees slight improvement in air quality, annual report shows