Just like any other training, consistent, incremental improvements will get you where you want to go. Get yourself moving. Cycling is great, but find other activities as well. At least an hour a day of activity is essential, but don't go nuts. Listen to your body, not that little voice that says "I'm tired, can't we sit in front of the TV eating donuts", but rather pay attention to the difference between being tired and sore and being overtrained or injured.
Counterintuitively, not eating is the poorest way to lose weight and the most likely approach to fail catastrophically within the first days or weeks. I suggest that you start by making an honest appraisal of what and how much you eat. Keep a record of your food consumption including portion sizes and count the calories you consume. I know a lot of people who think "I don't eat that much" my former self included, who are shocked when they see an accurate account of a week's consumption. An acquaintance of mine took my advice and found that while his meals were quite balanced and reasonable, he was consuming close to 1,000 calories a day in sodas and coffee drinks as well as a few coffee break snacks. He had estimated his daily average intake at 2,500 calories and found it was actually closer to 3,200.
There is a lot of controversy over whether or not junk food is truly "addictive" in the physiological sense, but it can be a very hard habit to break. Make changes in increments, I found that improving my breakfast made a huge difference to how I ate for the rest of the day. When I went from a donut and cappucino on my way to work, to a bowl of oatmeal, lowfat milk, and a hardboiled egg, I found myself skipping the morning coffee break (which usually included cookies or something equally as nutrition free) and being less hungry at noon. Not phenominal, but it probably cut 200 calories out of my morning and was better for me.
Over time, I cut the amount of starchy carbs like potatoes, bread, pasta, and rice in half and switched to whole or multi-grain versions and added more non-starchy vegetables like peppers, onion, beans, eggplant, mushrooms, squash, pumpkin, and leafy greens. I still enjoy a good plate of spaghetti, I just use a multi-grain pasta and load my sauce with chopped vegetables and lean meat. The whole and multi-grain pastas have improved a great deal over the past decade and I find that there are some that I like even more than traditional pasta. My advice is to avoid the carb control type pastas which use a modified non-digestable starch to reduce the net carbs. Expanding on that, I avoid all non-foods intended to replace food for the sake of reducing calories. I find that I'm better off using smaller amounts of the real thing or real food alternatives rather than fake, calorie free, non-foods. For example, if I want to sweeten my oatmeal, I'll use a tablespoon of honey or real maple syrup rather than an artificial sweetner.
When I feel the need for a treat, I like to ride my bike to Subway or the local coffee shop and get one cookie and a milk which I then take with me to enjoy on a bench in the park before I ride home. This was a big change from the days when I considered a box of a dozen cookies from the bakery to be single-serve and would wash them down with a huge glass of milk while sitting on the couch in front of the TV.
I'm not saying this is the "right" way but if you find any of these suggestions work for you, great. More important is to start making positive changes. Once you start, it gets easier with time and continued commitment and effort. For most people, huge changes overnight don't work long term, it has to be a process that involves both physical and mental adaptation.
Good Luck
