There are many things that impact your health and lifestyle according to the diet that you have.
Eating too little protein can cause a condition called KWASHIORKOR. This leads to a swollen stomach which is quite evident. This mainly happens in developing countries as there is a small amount of protein rich food. There is also no money to invest in the food.
You can calculate how much protein you need a day. This is know as EAR (Estimated Average Daily Requirement). It can be found out using this calculation:
EAR (g) = 0.6 X Body Mass (Kg)
So lets say that you weigh 60 kgs. It would be:
60 X 0.6 = 36g