Better to loose the weight.
Prior to my marriage, I once was in a relationship with a man who was chubby but in the process of loosing weight when we began dating, and he achieved his weight goal. Unfortunately he gained his original weight back and then some.
You would think the pressure to loose weight came from me. Unfortunately he had his own issues with it and his jealousy and insecurity sabotaged the relationship. He beat himself up over it. There were a lot of practical limitations that were introduced into our relationship because of the weight gain that didn't meet the eye. He literally began to resent me because of his weight gain. Strangers would often mistake him for a relative instead of a partner based on the disparity in our physical appearances. I’d like to tell you being supportive, and encouraging without trying to change them has a positive impact, but that wasn’t the case for me. It doesn't matter how much potential a relationship has, if your partner has a major insecurity about something to the point where they don't believe they deserve you, then the relationship is doomed. You need to be secure in the areas that are important to them and you.