Unless you actually have Celiac disease and a true allergy, gluten-free is just a dying fad unlike that of the fat-free fad.
Bottom line is that if you want to lose weight, you cut your caloric intake. That's all there is to it. These fads seem to work because while people are following these fads, they actually believe it or not.. WATCH what they eat. Also people eating gluten free area also eating less carbohydrates. Carbohydrates rare a fast burning energy, so unless you're really active all of that bread, rice, pasta, and beer is going to end up lining your gut and waist.