Doing long endurance training sessions is only one part of the picture if you are looking to drop weight in order to improve your strength (or power) to weight ratio. It is a common belief that if you train for long periods of time at a lower intensity, you'll burn more fat and thus lose weight. It is true that you burn a greater percentage of fat at lower intensities, and that at higher intensities you burn a greater percentage of carbohydrate. However, training at higher intensities allows you to burn a greater number of calories overall, so that ultimately you will actually burn more total fat (even if the percentage of fat usage is lower).
So, one of the keys to dropping weight is to incorporate some different training intensities into your program. For example,
No matter how hard you are training, you also need to pay close attention to your nutrition if you want to achieve your optimal weight. Just because you are training hard doesn't give you license to eat whatever you want; it's an unfortunate fact of life that it's a lot easier to take calories in than it is to burn them up. While it might take 30 minutes to burn 300 calories, it only takes about three minutes to take them in, say in the form of a candy bar!
That doesn't mean that you should severely restrict your food intake. You need to make sure that you are getting enough calories (particularly in the form of carbohydrates) to fuel your workouts. It's important that you have something to eat prior to your workout, particularly if you're working out first thing in the morning, as well as taking in about .75 grams of carbohydrate per pound of bodyweight in the first 30 minutes after your exercise is done. If you're exercising for longer than one hour, you'll also want to be ingesting some carbohydrate (between 30-60 grams/hour) during the workout.
Throughout the day, pay attention to the foods you eat. Look for foods that are nutrient-dense, like whole grains, lean meats, and fruits and vegetables, and avoid foods that carry empty calories, like candy and high-fat foods.
Finally, if you feel like you carry too much upper body weight, don't spend too much time in the weight room. While weight training can be beneficial for endurance athletes, there's a point at which it becomes too much. You can maintain good upper body strength by spending 30 minutes in the weight room two times a week; use the rest of your training time working on your specific sports of cycling and running.