Issues involving bowel movements are common when starting a new diet, whether it be a very-low-calorie diet or another type of diet. Usually, changes in your diet will be accompanied by changes in your bowel movements.
However, continuous constipation or diarrhea is not good for you. Constipation during this diet can be caused by not consuming enough liquids, especially water. Diarrhea can be caused by drinking too much liquid.
Never try to drink your calories when doing a very low-calorie diet, as our bodies need solid food as well as hydration.