i know...even my vet said "all that food and no weight gain?!"...she eats a ton and runs a ton. then again she's always been very skinny and always had a good appetite. when i got her she was 13 weeks old and she weighed 12 pounds. she's only 45 pounds now.
Some boxers just run to the thin side, they have a very high metabolism..Before changing to a specialty food like that I would try adding some additional protein to her diet...Peanut butter and yogurt is a good start..Fill a Kong with it and a sliced banana, freeze it for a few hours and let her have at it...It's also a way to keep her busy for awhile. Try cooking a bit of white rice and adding it to her food too...
Has the vet said anything about maybe running a thyroid scan? I would still be concerned...I believe you said that Roxy was over a year? If so, she should already be on an adult food..A good "all stages " food would be fine for her...I have a thread in the nutrition section that you might want to check out. It's a list from the Whole Dog Journal and has all the premium foods listed..This all are very high quality foods and you might find something that would work better for her.
I've found that sometimes Boxer bitches are just hard to put weight on, until they're about five years old! If she's been eating that much and hasn't been gaining weight, then obviously that food isn't working for her; if she's over 14-18 months, you might consider one of the grain-free foods like Innova EVO, Nature's Variety Raw Instinct, or some of the Timberwolf Organics formulas; these are generally high in protein and fat (42%/24%), so are good for active dogs. I wouldn't feed Eukanuba if you paid me.
What type of food are you feeding right now? We had a white Boxer Roxie who died just before her fourteenth Birthday, she weighed 42lbs her whole life, she was just a peanut. Depending on what your feeding now, a different food would help Im sure. Canidae, wellness Innova, timberwolf.
I agree with Newcastle...A high quality, low/NO added filler food would be best for your young girl!!! It'll give her lots of nutrition with out all that crap to fill her up. You can also supplement with high protein stuff like peanut butter, egg (go easy here), chicken and beef...even rice (like samsonsmom said). Supplementing with foods like these adds nutrition and variety.
My Lilly is narrow (prefer the term narrow to skinny). Her vet said to add more protein to her diet (shes already on an excellent, rather expensive high grade food). She's very active (service dog and 3 kids to play with) and has been deemed a high metabolism girl (like her skin mom). She wighs 65 pounds (pretty normal for a Boxer bitch) and is on the tall side (22.5 in tall), which gives her the look of being narrow. Overall she has a typical Boxer look.
Try the new food and maybe supplement her a bit and see what that does, then go for thyroid testing if she doesn't pack on sme weight.