This composite image of brain scans shows two traits of a highly impulsive individual. The cool colors in the midbrain are indicative of a decrease in dopamine receptor levels while the warm colors show elevated levels of dopamine in a different part of the brain called the striatum.
Joshua W. Buckholtz and David H. Zald
A group of teenagers take a morning jog at the Wellspring Academy in Reedley, Calif., in 2009. The school specializes in helping teens and college students lose weight. A new study shows teens who remain obese risk a lifetime of chronic health problems and poverty.
Justin Sullivan/Getty Images