Basically if you are having trouble eating enough, get rid of a large proportion of supposedly clean foods. Go for high GI carbs, high energy density, higher fat protein sources, good fat sources added in (peanut butter is excellent), and eat often. Try liquid meals, with added fat, chocolate MRP with peanut butter tastes good mmmm, i hate dieting.
While I wont advocate unlimited saturates, a raised amount will make it easier to eat more calories.
Oh yea, pizza tastes good, and has bulk calories, protein carbs and fats. beer is a good addition to it, honest.