First look at your food intake. How you eat is important in addition to what you eat. Smaller potions 4 to 5 times per day. Make sure you drink a lot of water. try and avoid sodas , tea, coffee. Weight loss should be gradual to give your body time to adjust.Mix in some type of resistance training in addition to sprinting, weights,bowflex, total gym etc. Resistance training has been proven to continue burning calories long after you stop the workout. it will compliment sprinting. Be patient. You will hit flat spots here and there. You may not shed a pound at times. Don't worry keep up the training as you are getting stronger and more fit. You will find your stamina will increase. Be consistent. Good luck