Many people erroneously assume that the more calories they can "burn" on the bike, the more weight they'll lose. The error comes from the fact that when we exercise hard (near LT) we metabolize almost exclusively carbohydrate and very little fat, while at lower intensity, the fuel mix includes a lot more fat.
Any carbohydrate you metabolize has to be replaced before you can ride strongly again, so hard rides do very little for weight loss. Fat metabolized during exercise does not need to be replaced, so riding at an intensity that actually uses fat is the way to go if you are using exercise for weight loss.
That means you want to ride relatively lower intensity to lose weight.
There's another common misconception related to exercise intensity and weight loss that comes from the sloppy way some research has been reported in the media: After an exercise session the body continues to metabolize more fat, even after you are no longer exercising, than it would if you had not exercised.
The research that showed this found that the exercise had to be "intense" to get the effect, but remember that when we are talking about sedentary research subjects, "intense exercise" might not be exactly what a trained cyclist would think of as intense.