Recent research helps answer this question. Diet-related diseases include heart disease, some types of cancer, stroke, type 2 diabetes, high blood pressure, obesity, and osteoporosis. Some children are undernourished. Even moderate undernutrition can have lasting effects on children's growth, development, and school performance.
Some children have problems with overnutrition.
The Centers for Disease Control and Prevention reports that 5.3 million young people aged 6-17 years are overweight or obese.