I want to know which type of bicycle is best for weight loss.
Whichever type you will ride the most. If you like to go off road, get a mountain bike. If you plan to stay on the roads, then a road bike or hybrid will work well. Make sure the bike fits you well and is comfortable. Make sure it is a good quality bike that won't break after 1000 km. A bike that's sitting in your garage because you don't like it or because it was cheap and didn't last will not help you lose weight. Any type of biking combined with a proper diet will help you lose weight, provided you put in the miles.