Could someone suggest some fat free foods?

Yes, you are absolutely right about the healthy eating habits. It helps you in long term plan for fit and healthy body. Curbing hunger cravings is very easy but curbing your hunger craving with healthy food is a tough job. I can suggest you some fat free food which could help your son in overall fitness. Well, in vegetables he can try anything. Because they carry tiny amount of fat. The vegetables which carry only traces of fat are cabbage, potatoes, tomatoes, pumpkin. He can definitely include vegetables in his diet plan. Also fruits are essential for overall fitness. Try to include as much fruits as possible in the breakfast. That is the best time for the fruits consumption. Then there is egg white which is fat free. Most of the dairy products contain fat but if he will try non fat dairy products such as skim milk, fat free yogurts, non-fat cottage cheese.If he wants to gorge on sweets, then gelatin desserts are great option because they don't have any fat and are very low in calorie content. In liquids there are water, tea, coffee which contain no fat. He can also include these liquid beverages in his diet plan. Hope you like my suggestions.