My feeling is that Intermitant fasting would be better. Eat during an 8 hour window. Remember you have to eat at least 350 calories when You take your meds. shoot for 1200 calories for the 8 hour window.
Sugar is not your friend so slim fast is full of sugar.
My suggestion to you is to eat regular food.
Sorry I know this is an issue for you, somehow you must eat real food.
You could make delicious healthy smoothies in the blender.
bizi