Remember that calories, while important, do not equal nutrition. The addition of whey or soy based protein powders, as well as amino acids in powder form would help. Check the labels of the shakes for total vitamin, protein, etc. content, and add from there. Of course natural ingredients such as vegetable juices and blended fruits (not citric) also might round things out. Don't forget just plain water. People who don't like to swallow frequently don't get enough, and this can cause serious side effects.