I don't think you're going to loose much weight with a one day fast or even a liquid fast. You can't have a good cleanse if you introduce solids into the system.
I am very petite and like you I cannot afford to severely restrict my calories for a detox. One step you could take for a good colon/intestinal cleanse is to mix psyllium (a fiber) and bentonite with 4 - 8 oz. of water and drink in the morning on an empty stomach. If you can try to eat raw vegan and take the drink for a 14 - 30 day cleansing. You can find psyllium & bentonite online. Follow the instructions on the product package regarding how much to use but make sure you drink the mixture very quickly. Bentonite "swells" and can become too thick to drink if you let it sit too long (I'm talking under a minute for the stuff I have used). Hope this helps.
