“How can I help my obese child?”

The best place to start is with your pediatrician to look at labs to see if there is a pysiological reason for his weight (i.e. insulin resistant). The next step is working with a bariatrician in your area who sees pediatric patients. You can find a good bariatrician through www.obesitymedicine.org. What you can do right now is to cut back on his carbohydrates and take all sugar out of his diet.