If he takes proper meals, what type of food does he eat?
Sometimes, it's a case of they eat what they like and they rather not experiment with other food. I find that in the case of my 4yo niece, she's very suspicious of all new foods or veggies we want to give her.
So most of the time, I will describe the texture telling her it's sweet or crunchy etc and coax her to take a small piece or spoonful. If it doesn't work, sometimes I'll give a similar portion to her younger 2yo brother to eat -- if he munches happily and wants more, then she'll try.
Other times, she'll use the excuse "I'm full already" to stop me from feeding her more of the food she doesn't like.
So in your case, why dont't you try giving less of milo and bread, and give him other food? Maybe chinese carrot cake or ham and egg toast etc?