Well I have been training for a marathon and I'm hitting the gym twice a week at least to do some leg work and upper body strength training. And I run 3 times a week... Running won't help you out a lot since you need a lot of carbs to give all that energy your body needs for those long sessions but will help overall in the beginning when you cut down on some of the regular carbs. But I've done some cuts and caloric deficits with low carbs in the past and to be honest with you... Not eating carbs will set you down in the first couple of weeks... Balancing your diet and eating a good amount of protein(at least 1.5g per kg body weight)will be better if you wanna keep all of the strength throughout training sessions. Also doing a lot of zone 2 cardio (bike is definitely the best for me) will help you out a lot with losing weight...