Childhood obesity has been a matter of concern now.. Its good that you are starting to think on these lines early.. the earlier we think of it its better...
There are two things you need to keep a check one is activity level and other is diet....
Speaking of diet
If you want a specific diet just give me details - veg/ nonveg, his weight and height, if you give me what he eats daily( 24 hr recall) with the quantity he eats. I can suggest a diet which will be specific to your son but anyway you can follow these guidelines....
1. cut down on his calories by avoiding fried snacks in your diet. - Its better for all of the members to follow the same diet as healthy eating is good for everyone
2. avoid using sugar. as sugar is just empty calories which is not even good for health otherwise.-If your child has a sweet tooth gradually wean him of from sugar you can use jaggary/ honey which are heathier options..but limit them too..
3. Avoid cheese, butter, ghee in preparations.
4. Avoid giving commercially prepared snacks like chips, wafers, sweetened juices, chocolates, cakes, pastries, burgers, pizzas, fast foods, chips, papads, etc .... Try making healthier home made snacks..
5. Try giving smaller and frequent meals since children tend to eat more if they are very hungry.. but don't make the snacks very oily.
6. Encourage him to eat plenty of fruits and vegetables...Encorage fruits more than juices.. But in summer you can give juices but limit use of sugar....
7. Snacks can be vegetable upma, soups, maccaroni without cheese. vegetable salads, fruit salaads. vermicilli.. steamed momos. Make them look more attractive at the same time.. And try not to repeat the same snack every day.
8. Use dals, whole grains, channa,rajma,etc... Use atleast two types of cereals say wheat, ragi, oats,bajra etc in the diet.
Increase his activity level by putting him on active sports like basket ball, foot ball, volley ball, swimming where he can build more muscles and it also helps him to grow tall. Don't encorage sitting on computer, tv or sitting games for long period of time.. Take him to park to encourage outdoor activities., weekends encourage more of outdoor activities..