Went gluten free at my house for quite a while. Nobody lost weight. Ice-cream, chocolate, potato chips, GF pizza crust, all kind of GF junk food out there if you look for it.
Yes indeed. A lot of commercial GF food is, if anything, higher in fat and sugar than the "regular" gluten-containing equivalent. Just because a product is "free from" something-or-other (whether gluten, lactose, nuts, whatever) doesn't mean it's healthy.
We've gone GF at our house because my wife has coeliac disease. But we use very few commercially-prepared GF products; we cook at home from basic ingredients, and simply avoid the gluten-containing grains.
If you basically went gluten free by relying on products from the supermarket "free from" section, I can imagine it's easy to gain rather than lose weight.
Not going to say it works for everybody. I was having a lot of GI issues and was diagnosed with IBS. Decided to try GF before committing to taking medicine 4 times a day, indefinitely...and it just happened to work.