There are some good German sites on cycling with articles on fitness and losing weight, like www.fitforfun.de. The articles at this site are not available in English, but you could get the general idea by feeding the text into an on-line translator. Search the site for “Fahrrad” (bicycle) or “Fett” (fat). The results give articles related to fitness and weight loss through bicycling.
A recent find was at this link. It is similar to other things in this forum related to maximum fat burning during longer rides and at an optimum heart rate of about 70 percent of maximum. The author suggests finding maximum heart rate by first taking your resting rate and noting it. Then ride as hard as you can for 30 minutes in an open, low traffic area. During the last minutes of the ride take several pulse readings and average them. This will serve as your maximum heart rate.
Calculating 70 percent of you MHR gets a little more invovled and worked out to about 80 percent of my MHR as I had understood the process. Here is the author's formula: MHR minus resting pulse multiplied by 0.70 and add back the resting pulse. A suggested time for riding was not given, but I would expect 30 to 60 minutes would do. First increase the number of times per week you ride, then increase the duration of the rides, and finally increase the intensity of the workout.
In another article in this series, the authors say results are better when they do not automatically reach for an energy bar on a ride. Weight loss will be faster. Just before a ride drink a mug of black coffee--no sugar, no cream. The caffiene stimulates fat burning. Eat nothing, otherwise the blood sugar rises and fat burning slows.
Another German site with articles in English is at: http://www.cycling-insider.com/ A registration is required. A quick search as a guest turned up articles and posts in German, not English.