More than two-thirds of America's youth are ineligible to join the military due to physical, behavioral or educational issues, according to the Pentagon. The Army requires recruits to hold a high-school diploma or GED, and meet height, weight, fitness, drug use and other requirements. The biggest single reason for failing to meet the requirements is obesity, which has become a national security issue. By 2020, the proportion of eligible recruits could fall to just 20%, with only two in 10 young people able to qualify for service. Military leaders have called for expanded early childhood education and access to healthier food to address the issue.