see if you can find a used copy of the book "if this is tuesday it must be Chicken" It puts different foods into categories of rotation so you never get reactivity from foods 2 days in a row. It is also really helpful with helping to identify which foods and types of foods trigger the most impulsivity.
Plus that way you can still buy whatever food is on sale that week, it is just the order and rotation of the foods you modify, so it doesn't require buying anything else.
It helped my brother A LOT with impulsivity/ocd/hyperactivity.
:) hope something helps :)
My two cents is that the most important thing is what not to eat: dairy and wheat being the first two things to avoid to see if that helps, and obviously to avoid the sugary sweets and the simple carbs such as white flour and too much fruit and try to get as many colored vegetables in the diet as is possible. Organic is somewhat more expensive, but it avoids a lot of added allergens and toxic chemicals that excite the immune system and the liver and the hormonal system. And avoid processed foods, with all their hidden stimulants such as msg and certain soy and corn derivatives and chemical preservatives. He's probably not going to like it, but there it is.