145 pounds, 170cm tall, female. been doing cardio & weight lifting for 2 months with good diet, goal is to lose body fat and gain muscle. what is the science behind doing weights before/after cardio? will it really affect my gains/weight loss either way?
Generally, you should identify which exercise is more in line with your goals, and do that one first. For instance, as rowers, my team will row first, and lift after. This allows us to perform the row at 100%, while the lift, performed while tired, lacks some intensity and focus.
In your case, it would seem like lifting is more in line with your goals, as you don't state a desire to improve cardio capacity, only to lose weight and make muscle gains. By lifting first, you will maximize the amount of muscle you gain, and can adjust to any decreased cardio intensity with a diet change. In the reverse scenario, you wouldn't be able to adjust your diet to make up for a reduced lifting intensity.
Another factor the order depends on is the general intensity of your cardio work. Above, I'm assuming it tires you out enough that it would impact your ability to lift; however, this may not be the case. If you feel that you can still perform the lift at full capacity after cardio, then the cardio could serve as a great warm-up for the lift, and you might be better off doing cardio first.