With a couple - you both win whatever because you benefit from each other's success.
I really wish that my husband would join me on our amazing weight loss journey... His BMI is still in the very high 50s and we both know that this is not good for his health... He is older than his father was when died from a heart attack due to his severe morbid obesity...
It all means that there is a heck of a temptation in the house too... Last night we sat on the sofa together eating cheese and biscuits while watching television. We must have eaten a ton of calories - just because they were there. It is really hard not to eat something yummy when it is right in front of you and being handed to you (or fed to you by someone that you love!!!)
I think that it is brilliant that you are doing this together.