It’s right there in the article, first paragraph:

Being overweight or obese causes hormonal changes, which accelerate children’s development. Obese children grow faster, so they tend to be taller than their healthy-weight peers. But obese children have a greater risk of disease in later life, including diabetes and heart disease.

Without further research on my end what this means to me is “poor children are more likely to be obese and reach their, presumably shorter, adult height earlier in their childhood”.