Could it affect my health?

Malnourished people are generally very unhealthy.And if you are trying to lose weight this way, it's a bad idea: as soon as you reach your goal, you will more than likely eat more than you are supposed to instead of returning to your baseline. Additionally, your body will be used to starving so it will take any extra calories you consume and turn it into fat so that next time you are malnourished you are less likely to die.