overeating

my son is 3 years old and is constantly hungry he has 3 good meals a day and always has fruit and veg at hand if hungry but he is never satisfied and is always demanding and saying he is hungry even when he is busy doing activites can you suggest anything too solve this?

[JDRF Volunteer CB]

Signs of diabetes are excessive thirst, frequent urination, blurred vision, mood changes, and feeling lethargic.
I do think if you are worried or suspect diabetes you should make an appointment with the pediatrician and voice your concerns and let him know what has been going on with your sons eating habits.   You don't mention if he is gaining a lot of weight with the food he is eating.  Usually when a child is diagnosed with diabetes there is weight loss not weight gain.