Brown sugar can lead to weight gain or obesity: People who consume the most sugar are by far the most likely to become overweight or obese. This apples to all age groups. Many studies have analyzed and link sugar consumption and obesity, especially in children.
Sources:
http://www.sciencedirect.com/science/article/pii/0306987783900956
http://link.springer.com/article/10.1007/BF01830725
http://cebp.aacrjournals.org/content/6/9/677.short
https://en.wikipedia.org/wiki/Sucrose
http://www.sciencedirect.com/science/article/pii/S0306452205004288
http://www.sciencedirect.com/science/article/pii/S0149763407000589
http://www.sciencedirect.com/science/article/pii/S0140673600040411
