Manas, you can get enough protein without meat. I'm not too bukled up, but I do work out, and I'm fairly bigger and stronger then the average person. My diet is very simple, my main foods are whole-grain wheat flatbread and legumes- lentils and beans, from animal products I eat an egg, two or three a month, and drink a glass of milk or two a week. Besides that I eat only cereals (millet, rice, etc.), veggies and fruit, and I get enough protein for working out.
Also, my advice is to shun the gym. Exercise at home- squats, back extensions, twisting sit-ups, push-ups, pull-ups and the deadlift can all be done at home, they they exercise all the muscles, and are enough for everyone that is not a bodybuilder. If someone doesn't want to buy a home pull-up bar, he can use pretty much any park, also if one doesn't want to buy weights he can deadlift large stones he finds while out for a walk/run, but if someone can't or won't do those alternatives either- the pull-up and deadlift can be replaced with good-mornings, inverted row and elevated-feet inverted row, which can be done at homea. Also shun the gym workout program. Exercise every other or third day, and also make long pauses, e.g. work out for a couple of months, and then pause a month. Exercise hard (slow moves, no muscle rest in a series), use proper form (this is also a mindfulness exercise
), sleep enough and eat enough, and you can not only stop being thin, but also get reasonably big and strong.