Your body will start to get weak. The body does need some fat. It will be like not eating enough carbs, you can do it for a small amount but then your body will find the fat that it needs, and your organs are made of fat , and when you go back to eating fat your body will store all of it.
Fat is crucial for bodily functions, brain and heart health, and the absorption of certain vitamins. Fat levels that are insufficient may affect these issues.
Your body will die down and be extreamly week also leading to extream hunger and anerexia