I have 1600cal diet routin and i execise 1h and 30 min 3 to 4 times a week. but i dont lose weight,why?!

Need to do a: Through tracking of how many calories you are realistically consuming, along with how many calories you are actually burning(this includes estimating your resting metabolic rate - how many calories you burn just "living" + what your burn from your activity levels). Do it for just even a week and you may really be surprised what your actually caloric values are. Need to be very meticulous.