Yes, it is unreasonable to lose weight like this. You should eat some nutritious and digestible foods early, such as cereal and milk, and then eat some fruits. Eat normally at noon and be full at six or seven. Do not eat too much. Eat apples or boiled vegetables in the evening, and add some small exercise. In this way, you can avoid malnutrition and lose weight. Losing weight depends on persistence, which is a slow process, not a day or two without eating.