Story highlights Willie and Angela Gillis weighed 492 and 338 pounds respectively

Through diet and exercise, the couple dropped more than 500 pounds

They credit their strong relationship with helping them lose weight

Marriage, any good therapist will tell you, is a balancing act.

For Angela and Willie Gillis, the act is easy. They've been best friends for more than 10 years, married for three. Their individual strengths balance the other's weaknesses.

They credit this sense of balance with helping them lose a combined 500 pounds.

"Everyone needs that one person to help them through, to talk to and someone who will hold them accountable. That person has been my husband," Angela writes on her blog, WeBeatFat.com

A few days before their first wedding anniversary, Willie woke up and told his wife, "I'm tired of being big." He had just gotten back from visiting his newborn goddaughter and was scared he might not live long enough to see her grow up.

"For years I had been reading up on 'This is how you lose weight -- nutrition, exercise,'" he says. "I wanted to see if I could do it."

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That was January 2011. He weighed 492 pounds.

His wife didn't have to think long about joining him in his quest.

Growing up, she never thought she had a problem. "You know how (New Jersey) Gov. (Chris) Christie said, ' I'm the healthiest fat person '? That's how I was," she remembers.

She was fairly active, but she loved food. If she was happy, she ate. If she was sad, she ate. If she had the best day of her life, she ate chili cheese tater tots.

By January 2011, she weighed 338 pounds.

Willie had recently moved to Angela's hometown of Beaumont, Texas -- a city so enamored with fried food and lazy summer days that it was named the fifth most obese city in the nation in 2012.

Even in the growing population, the two felt ostracized by their size.

"It's amazing how people will look at you when you're fat," she says. "We just didn't want to be those people anymore."

So, her husband took out his research and created a plan. The couple started hitting the gym six days a week. At first, all they could do was walk 30 minutes on the treadmill. Slowly they increased their time, until she was running and he had walked off almost 150 pounds.

In the kitchen, Angela was the expert. She loves to cook and quickly learned to make healthier versions of the couple's favorite meals. The Gillises started eating a solid breakfast of steel cut oats and fruit or veggie omelets. They packed diet-friendly frozen meals for lunch and low-calorie snacks like yogurt, carrots and apples. Dinner was -- and still is -- lean meats and vegetables.

"We haven't had fried food in two years," she says.

That doesn't mean they don't give in to cravings on occasion. Willie used an iPhone app to track his calories and saved a few every day for a weekend treat. Angela had to continually ask herself if she was eating something because she loved it or because she just loved eating. Through it all, they kept each other accountable.

"I never wanted to come home and say, 'This is what I did today,' because I didn't want to disappoint him," she says. "And he didn't want to disappoint me."

Eating out was their biggest obstacle. Even light restaurant meals can be loaded with sodium and fat. It didn't bother the Gillises to go out and not eat anything, but it bothered the people they were with.

"Most of the memories we had with our friends (were) sitting down, going out to eat," she remembers. "Food is a very social thing."

They ended up isolating themselves a bit, and met new friends through their gym. They took photos of their progress, seeing a visible change each month as they weighed in.

Life for the Gillises is now full of activity. She teaches spin classes at the gym and recently completed a half marathon. She's lost 200 pounds, going from a size 28 to a size 0.

"I'm stronger. I believe more. I go after things I want more. I was never, ever a risk taker, but now I take the risk," she says.

Willie joined a local running club. He has lost 300 pounds and gained a world of self-confidence.

"A lot of people give up -- they end up quitting because they're not doing something right. You have to take what you messed up on and try to make it work for you," he says. "Once you learn it, it doesn't take much to keep it going."