I cooked 1/2 package of frozen spinach in about 1 cup of water with some salt added. Then I made one of the soup packets with 1/2 cup of water and a chicken boullion. I let both cool until only warm. Then I combined them (keep the water in the spinach) in the blender until smooth. (Be careful it's not too warm or it will blow the top off the blender -- learned THAT one the hard way.

This was absolutely fabulous - it was kind of like a cross between creamed spinach and a cream of spinach soup.
Since 1/2 a box of frozen chopped spinach is 40 calories - I don't think it will interfere that much. And I'll just decrease the amount of my veges at my lean and green to compensate for the extra calories here.
Give it a try and let me know what you think!