There is no shortcut. Eat less, exercise more.
There is no reason you should be terribly sore the day or two after you exercise. Increase the duration of your exercise gradually. If you do five minutes today, do six minutes tomorrow. And seven minutes the day after.
Once you get to a reasonable duration, start increasing the intensity.
I use the Polar FT-80 heart rate monitor/trainer to manage my training duration and intensity and have had tremendous success with it. It is a very intelligent unit and 'knows' when to push you and when to take the intensity down a little.
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Measure twice, cut three times, start over. Repeat as necessary.