Obesity among young people is a growing problem in the United States — and so is malnutrition, according to two new studies that look at how children eat, and how they don’t. In 30 states, nearly one out of every three children is obese or overweight, according to a study released July 1 by the Trust for America’s Health and the Robert Wood Johnson Foundation. The study finds similar concerns and rates for U.S. adults. On the same day, another report was made public with a different set of numbers — in 13 states, one out of every five children under the age of five go hungry. That report, released by the nonprofit Feeding America, documents the impact of hunger not just on the child, but on the whole nation.