There is no good way to tell the one you love that she is fat. Sometimes it is best to just come out and tell her that you are concerned for her health, that her weight is increasing and asking if she is feeling allright. She quit jogging? Do you jog? Going to the gym together is one way to address the issue. SInce you live together, does she do the grocery shopping alone? If you do it, or at least go with her, you can grab low fat/ low calorie foods. If you get concerned with what you eat, maybe she will follow suit. On a night that you will both be staying in, make some popcorn (no butter), and pop in the movie "Supersize me". I guarentee that it will change the way you look at food. One last tactic. If she doesn't already own one, buy her a full length mirror. Women love them and nothing disgusts a person more than seeing their own body from head to toe. Good luck. Remember that being overweight does cause serious medical problems and your concern is not simply cosmetic.