This.
Don't make it about her. If it's about her comments hurting your feelings, she will realize what she's doing and stop it. Sounds like you have a good relationship, so she won't want to do something that hurts you. She will get used to the new you.

Trying to get her to lose weight is a whole other matter, and very tricky as all these posts show. Women are bombarded with propaganda about what we're supposed to look like all the time, so many of us are insecure about it. I don't envy you guys in this one! How you go about this depends entirely upon the personality of your wife, and only you can know that. Some women thrive on competition, others find it a huge turn off and they won't even try. You can try doing things together (sounds like that may work) or encourage her to ride with friends or other women if that appeals to her more. But I would avoid the appearance issue altogether, there's nothing you can say there that won't hurt her, and it isn't anything she doesn't already know. Tell her you want her to be active with you so you can spend more time together. My husband and I ride together all the time, as well as a lot of other sports we both enjoy. It's good for the relationship.