There are many reasons that someone might follow a vegetarian diet. It could be on religious grounds, on ethical grounds about the mistreatment of animals raised for the food industry, because of concerns about the safety of meat, it could be that meat is too expensive to eat where they are in the world, or a whole host of other reasons.
Then within the broad term of ‘vegetarian’ which most people use then there are distinct classes based on what people will or will not eat; some will eat eggs, milk and honey (ovo-lacto vegetarians), some will eat eggs but not milk (ovo vegetarians) or milk but not eggs (lacto vegetarians), or none of the above (vegan). There are even raw vegetarians who refuse to eat food which has been cooked.
Around the world vegetarianism is thriving, with approximately 399 million* people in India alone following some sort of vegetarian diet, although in the US that number drops to about 12.4 million*based on a survey done in 1992, and nowadays almost every menu you see will have vegetarian options for people to enjoy. Those numbers are going to increase too as people become more aware of the way food animals are treated, and the price of meat continues to rise.
Of course the one thing that you need to understand is that you will have to eat some foods that will give you the energy that you need in order to do normal things in life. Foods like eggs are a type of protein and they will help to give you the energy that you need to live.
You will also have to use this energy and use it to exercise. Remember that in order to lose weight you need to have an elliptical machine that is going to give you the right amount of burn that you are looking for.