Wife gained major weight - how to convince her she is a hippo?

hi all. when we first started going out round 3 years ago, man she was really something. after we got married, she stopped working saying that she finally wanted to do her masters, and then all of a sudden she ends up doing nothing at all, just basically messing round. now, a year after our marriage, she is just so fat and repulsive i don't even enjoy going home because i have to be around that tub of lard. i weigh 160 pounds and am 6 foot tall. from the looks of it, she is probably edging towards the 180 mark right now. she even has the nerve to say she is 'probably' more light than me, pointing to her height. i would love to leave her, but i don't want to be known as the town man, which is how people think in my small community. can you guys recommend some ways i can convince her she needs to get off her fat @ss and actually start looking better and doing something productive?