Well - if you mean a treat such as a steak with sweet pepper, mushrooms, tomato and a green salad followed by berries and cream or you might like a few sticks of celery and cream cheese - you can have that no problem.
What it appears you can't eat is the heavy carbohydrate foods such as potato - probably bread, pasta, rice - maybe any grain including oats are going to be off the menu too, or severely limited, along with sweet or starch fruits such as bananas, grapefruit, oranges, even apples and pears.