Primarily because im trying to decrease my overall amount of fat. Look with running your body hates it to put it plain and simple. So the thought people have that is correct is when doing cardio you do exert your self of energy. Lets say you have a Basal Metabolic Rate (BMR) of 2000 calories. So if you were on a caloric defecit diet how would running help you? Your basically saying this "HEY IM malnourished! YOU KNOW WHAT SOUNDS LIKE A GREAT IDEA!? RUNNING 3 MILES! No thats sounds fuckin horrible! haha now I know you didn't say this but literally this is how you damage your metabolism. Your body eats itself and if you've been reading my previous comments understand this, it turns to muscle not fat. So if muscle is part of what makes your BMR why would you wanna do something thats going to make you reduce muscle?
How do you achieve fat loss through cardio? Well you cant be malnourished So if your BMR is 2000 and your cardio workout burned 250 calories. Then your body is going to raise how many overall calories it needs that day alone. Now here is the complicated part. When running not every calorie burned is the same. Fat loss this way depends largely on whats in your blood at the time you run and how hard you ran(your hear rate level) and what you ate. All of this determines where your body will pull its energy from, which is either glucose, muscle or fat. Now unless you time for all that planning fat is going to be the hardest to burn. So to get to fat loss from cardio training you need to consume an absurd amount of carbs to keep you from going catabolic. Now have you ever done a high carb diet? it really really sucks man. because if your doing it right you don't really burn more calories then strength training and its harder to hold diet. you get cravings for sweets which makes it hard as hell. All this not to mention that cardio yields a lower calorie deficit daily if your doing it right.
benefits of strength training/adding muscle? Well You burn at the time of activity, You burn at time of repair and new muscle adds to your BMR. plus it doesn't suck balls to do.
I disagree though. I lost a little over 100 pounds from running. One thing you never want to be is malnourished. While running you want to be properly nourished. I eat a lot yes, but that is to make up for all of the calories I burn. Also 3 miles isn't running far. It is all perspective I know what that is a really short run.
I have never had to have a high carb diet based on my exercising. I do eat a fair amount of carbs, but as you said your body needs it. I know all of our bodies are different, but I think running is a great way to loose weight. Endurance running i.e. marathon running isn't as bad on your body as you think if you run properly. If you have poor form, yes you get injured. Sure I have been injured from running but it is due mainly to increasing my mileage too quickly.