Can I lose weight just by weight lifting?
Yes & No. That's like saying can I lose weight by walking for 3 hours....and walking will indeed burn calories, perhaps 500 calories, but imagine what happens if you then drink a 650 calorie protein shake. Weightlifting is good exercise in that you not only burn calories exerting yourself but you also stimulate your metabolism for hours to follow (so you burn calories and keep on burning). Weightlifting also helps you retain lean body mass (muscle) when under a caloric deficit. While dieting up to 50% of weight loss is not fat but instead lean body mass...so weight training can help offset that.
Factually put, weight training is an important and beneficial component to any diet or fitness regimen...BUT weight training alone will not ensure you'll lose weight. The simple fact remains: if you eat more calories then you need, you'll gain weight...and conversely, if you eat less calories then you need, you'll lose weight. The size of your body is largely dictated by diet. And yes, muscle on your body requires calories (so they say muscle burns fat)...but again, if you eat more food then it's a wash.