I definitely think that it is important for you to encourage your girlfriend and not belittle her because of her weight gain. And by encouragement, I mean make a date out of going to the gym. If she used to be really into working out, help her to arouse that fire inside of her again. You never know what kind of effect releasing some pheromones together could have on your sex life. Joining a gym with a sauna or a hot tub never hurts either … a little post-workout heat can be just what the doctor ordered and instead of you arousing her, you could be arousing each other!

The two of you should also set up some sort of incentive/reward between the two of you where after one month, whoever has lost the most weight (hopefully it's her for your sake) must be pampered, showered, wined, dined and spoiled! Take her on a shopping spree! If you're ballin’ on a budget take her to forever21; if you're not, hit up Neiman Marcus. That way she can actually see her progress by the way clothes fit. Then, after hitting the store, wind down with some strawberries (gotta keep it healthy), whipped cream (low-carb) and red wine (it's low-carb too). This way after one month, your girl will be tighter and hotter and so will a few other things.

I think that women oftentimes forget that they were once sexy once they're in relationships. They feel like they don't have to look their best 100% of the time because they have a man and are not trying to gain the physical approval of other men.

One thing that you MUST not forget during the whole process is POSITIVE REINFORCEMENT. After the two of you have gone consistently to the gym and both been eating right for a week or two, COMPLIMENT HER! Tell her how sexy she looks. Let her know that she looks like she's glowing. And remind her that you are a lucky man to have her in your life. That way she sees how excited you are about her appearance and won't want to let herself fall back into a slump.