Too fast weight loss will make our body unable to bear too much changes, because such a speed will make our body lack of trace elements, and in severe cases, symptoms such as anemia may occur. For example, iron and protein in our body will lead to unhealthy state with the weight loss, so we can lose weight in the right way, not through hunger.
People who lose weight can increase exercise and reduce food intake, which is the correct way to lose weight, instead of letting our bodies lose weight quickly by not eating a certain staple food. In this case, just like disasters, earthquakes and landslides in our daily life, we don't have much time to protect ourselves because of the high speed, and so does losing weight. You can't just pursue speed without pursuing quality, which will be counterproductive.
There are no shortcuts around us, and there are often some shortcuts that can be reached at the expense of something. Just like we lose weight, fast weight loss is achieved with the loss of trace elements in our body as the victim.