first you're a young male. assuming that you're an average height of about 5'10" and you'll be physically active consuming 1 200 calories is way too low for you. i'd aim closer to the range of 1 500-1 700 cals per day. next up you really do need to eat higher quality food. quality is important for health as well as weight reduction. finally yes weight reduction will occur if you simply consume fewer calories and (hopefully) increase your physical activity. you can eat five candy bars all day and drop weight if that's all you eat. however eating junk plays havoc with your blood sugar levels and if it's high fat junk (eating one pizza all day) you won't be doing your heart any good as well. the best way to go is to strive for balance. you want healthy whole foods with some treats thrown in. and you want to stay physically active. why? activity makes it 10 x easier to sustain your weight reduction.
i'm a 21 year old guy trying to lose weight on a 1 200-1 500 calorie daily diet. does it matter what i eat? . does it matter as long as i'm eating fewer calories than i'm burning?