high sugar content would lead to lack of ketosis and severe hunger
possibly diarrhoea as sugar is an osmotic.
Lack of protein would lead to catabolic state in the body you would start to break down muscle, above and beyond "normal weight loss rate", for calorie use, leading to potential heart problems, weakness, lethargy.
Lack of minerals means you put your overall health at risk, same with the vitamins
Lack of trace elements means problems