I've just eaten a whole cake and my diet is bad?

It seems I can just fit anything in my stomach, though I only weight 114. Lately I've been eating one big meal per day, at breakfast or lunch, around 1300 calories. Then I can only have tea or fruit for the rest of the day cause I feel sick. Yeah, yeah, I know it's a crap strategy if I wanna be healthy but it's christmas and I can't help craving on all the sweets milling around the house. So, if I eat one big meal a day for, let's say, two weeks, whate are the drawbacks?