I agree with the concerns in this thread that 25lbs is an (overly?) ambitious goal in this timeframe.
And training for a marathon places a lot of demands on your body, and requires a lot of resources - both in terms of energy, and free protein to keep up with all the little repair jobs. Running a large calorie deficit to lose weight that fast is likely to compromise your training. I'd recommend focussing on one goal (weight loss or training) rathe rthan both simultaneously.
But in answer to your actual question, Spark will take care of all the math for you. Work out how many calories you are burning through exercise in a typical week. Then update your Spark Exercise Goals (accessible from the LH side of the Start page) to reflect that figure, and Spark will recommend a intake consistent with your needs. My advice would tod also update your target rate of weight loss to something more consistent with your training goals (eg. 0.5 lbs per week).
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.
| current weight: 178.0