Losing weight is like cutting down a forest full of trees. The best way to do that in this case is with some sort of cutting device. In this case we will use a diet as our cutting device. What kind of diet is akin to what kind saw you use.
A crappy diet is like using the back side of an axe. A well thought out, diet that you can live with for the rest of your life is like a chain saw. Riding a bike several days a week for a good period of time (over an hour) is like having a chain saw with a very sharp blade. You will cut down a lot of trees.
Remember that losing weight, like cutting down a forest of trees is a combination of things, as illustrated above.
I've ridden 20,000 miles in the last 3 years, mainly on unpaved gravel and dirt roads on my mountain bike. I am 37 years old, 6'2" and around 150lbs. I weighed around 200 when i started the diet and eventually the riding.
When i tell most people this, they always comment that they should start riding like that so they can lose weight. They just assume it is the riding that does it. In fact i lost most of my weight before i ever turned a pedal. I lost it by using a chainsaw to cut down the forest. Having a very powerful saw with a sharp blade helps as well.