I have found with cycling that it's tough to be on hard-core weight loss mode and do tons of cycling at the same time. For long distances/high intensity it's just very hard to fuel that on body fat alone, not to mention it's way easier to bonk if your brain thinks it's being starved of the glucose it needs to function properly.
I've been in weightloss mode, and cycling mode, again recently. I've gone as far as 43 miles on an empty stomach recently, but that was with watching the heart rate monitor fairly religiously and forcing myself to keep the pace down. Honestly I don't really like doing this, so in some of my rides I've eaten 200-300 calories of carbs shortly before a ride and then let the chips fall where they may.
I think there's a good reason why if you look at the various "mass builder" formulas they sell in the supplement stores next to gyms it turns out the primary ingredient is usually sugar of some sort.
At the end of the day, though, I think there's something to be said for throwing in some weight training to keep the fires lit. Yes, weight loss is just a matter of calories in vs. calories out, but calories out includes both basal metabolism and the actual calories burnt doing whatever exercise you're doing, and for most people, the calories burnt during exercise is a minority of all calories used in a day. Keeping the metabolism up is probably more effective for most people than doubling how long they exercise.
I don't eat tons of carbs these days, but after a ride that's been long and strenuous enough that I'm worried about my glycogen stores I'll make a sandwich from a sandwich thin (~100 calories worth of bread) and some turkey or something for protein. Some carbs immediately after strenuous exercise is a good thing. And for long enough or hard enough rides, some carbs during the ride is a good thing too.