Thrilled with wife's weight gain, am I weird or unethical?

My (36) wife (35) has historically been a very skinny lady who likes dancing and spending time outside. She's also always loved food, and as she's gotten older, her metabolism has slowed down. She put on a little bit of weight after the wedding and after she had a kid she ended up about 40 pounds heavier than when she started dating me. Sometimes she says she wants to lose weight and I always support her decisions, I tell her she is beautiful mo matter what, but her willpower fades usually a week after each decision to slim down. She has now gotten too big for her old fat pants and doesn't seem to care. I like the extra girth, but worry about the health consequences of being 40 pounds overweight. Should I put my attraction aside and support the weight loss more vigorously? Am I enabling her by telling her that I love her regardless of size? Frankly the sex is waaaay better now that she's plump and I think this factor is undermining her resolve to lose weight.