Sure, but if you only use water to cook, it will lead to malnutrition, severe obesity and constipation. If you want to cook with water for a long time, you can mix it with some high-protein and high-quality carbohydrates. If you want to lose weight immediately and quickly (3-5 days), you can just boil it in water. Although you will lose weight soon, most of it is water, so drink enough water every day.