What can be the causes of weight loss plateau and what should one do when he reaches that stage?

Familiarity: When you reach a plateau with your weight loss it is usually because your body has become accustomed to what you are doing. It is important to change up your diet and exercise routine to "trick" your body into thinking something is different . You can change your form of cardio or add in some light weight lifting . Good luck !

Resistance Training: One thing you can do to increase your metabolism is to build muscle. This takes training with weights or against resistance. While you might see a slowdown in weight loss, you should keep losing inches because you're losing fat, and that is what is important for your health (and how you look).