Just sit with her and advice her about what you feel. That shows you do care for her wholly. Advice her to take some time for herself too. It will help a lot. Ladies focus on the kids hubby and everything. So at times they forget to focus on their body, mind and spirit due to being exhausted taking care of home affairs.
Communicate in a way that will motivate her to make an effort to keep fit. Good diet and some activeness is required.