If you think you need to down plates of chicken breast or red meat in order to boost strength and build muscle, meet Marcella Torres and Derek Tresize. This vegan couple stands out in the world of bodybuilding not just because of their impressive physiques, but due to the plant-based approach they take to building such enviable muscles.

Tresize, a World Natural Bodybuilding Federation (WNBF) pro, currently stands at 5' 11" and a shredded 180 pounds. And Torres, who has competed as part of PlantBuilt-an all-vegan team of athletes-is 5'2" and a lean 112. And they really do have a vegan diet to thank, in part, for their bodies: "Before I became vegan, I was obese and completely unaware of how to eat healthfully," admits Torres. "My best friend gave me a copy of Diet for a New America by John Robbins about 15 years ago, and after reading it I promptly cleared out my fridge of every scrap of meat and dairy and never looked back."

Learned about the health and environmental benefits of a vegan diet-from the dramatic reductions in greenhouse gas emissions to the decreased risk of chronic conditions such as heart disease, diabetes, and cancer-kept her committed to the decision. As a biology buff currently in pursuit of her Ph.D., Torres knows good research when she sees it-and there's plenty of it surrounding a vegan diet done right. (Psst... Science says A Plant-Based Diet Is Ideal for Weight Loss.)

Of course, Torres never anticipated that her newfound approach to nutrition would have such an impact on her love life. Tresize and Torres (now married with kids) initially bonded over the subject. Tresize even admits he wasn't sold at first: "I thought vegans must be malnourished," he says. "I was so worried about losing muscle mass."

From Vegans to Bodybuilders

But the diet was far from something that malnourished the pair. Instead, it strengthened them. And the transition wasn't as extreme as you might think either. "I continued to eat vegan versions of the same foods I had always eaten-like vegan pizza and donuts­-and even with eating these transition foods, I still lost about 40 pounds," says Torres. (Try these 5 Steps to Ease Into a Vegan Diet.)

Soon both Tresize, a personal trainer, and Torres noticed that they were losing weight (in a healthy way). A once worried Tresize says it wasn't muscle mass that he lost either, but fat. "Even with all my athletic endeavors and fast metabolism, my body fat percentage had been stuck at about 12 percent for years," he says. "When I changed to a plant-based diet, it dropped to seven percent in about a month." But while they had proved to themselves that it was indeed possible to be fit and muscular on a plant-based diet, they wanted to do something else: shatter the stereotype of the malnourished vegan.

After all, as Tresize puts it, "In the mainstream bodybuilding world, the idea that animal foods are essential is still a long way from being dispelled."

So the duo decided to test their hands at competing on stage alongside bodybuilding competitors who followed a meat-heavy diet. Their goal? To win.

And win they did.

"Competing in anything for the first time is intimidating, especially getting up on stage and having your body judged while wearing next to nothing," says Tresize. "There were lots of nervous butterfly feelings, but stepping off the stage after hitting all the poses was extremely satisfying."

What was also satisfying? The surprised reaction of some of their meat-eating competitors, who were in awe of Torres and Tresize's well-developed physiques. "By the time of the competition, other competitors were practically eating nothing but meat and craving starches and fruit because they're convinced they need to eliminate those foods in order to step on stage," says Torres. "When they meet us as vegan competitors who've been eating a normal amount of these foods and see the same-if not better-physical results, not to mention not looking nearly as haggard or dehydrated, it raises a few eyebrows!" (Read about A Day In the Life of a Bikini Competition Winner.)

How They Pulled It Off

To prepare for their first competition, both Torres and Tresize kept their training routine mostly the same, yet consistently added in more cardio in addition to eating progressively less food to shed body fat. "Being that I was preparing for my first competition as a way of getting back in shape after having my first child, I needed to get from 29 percent body fat to 12 percent, which is a big decrease," says Torres. The key to getting her there safely was to actually increase her food intake for several months (to fire up a sluggish metabolism), she explains. In fact, Torres only reduced her calorie intake or increased the amount of cardio she was doing if she plateaued. Otherwise, she avoided any drastic changes.

They also focused on affordable meals-which didn't sacrifice taste or nutrition. "One of the greatest benefits of a vegan diet is how affordable staple items like rice, potatoes, and beans are, especially if you buy them in bulk," says Torres. "If you keep your favorite fruits, vegetables, seasonings, and sauces on hand, you have the makings for many easy and frugal meals, which can easily be prepared in advanced and stored for the week." And though they transitioned to the diet with fake meat and vegan cheese products that are processed, now they limit those foods to no more than two times per week. (Try these 6 High-Protein Vegan Meal Ideas.)

When the competition was over, word spread still. "We were getting more and more interest from people who have been competing and eating the standard high meat diet and consequently have had a health scare or who just feel terrible physically as a result," says Tresize. So they decided to write a book-The Vegan Muscle & Fitness Guide to Bodybuilding Competitions-in an effort to educate those who were interested in following in their footsteps. "It contains all of the guidelines, calculations, and training protocols that we have used successfully with hundreds of clients," says Tresize. This includes shedding light on the fact that a high-carb diet is just fine for fat loss-even in the last stages of competition prep.

Want to try your hand at a day in the diet? Here's an example of their plant-based diet (which you can follow too!):

Breakfast: Overnight muesli with coconut yogurt

Lunch: Nicoise salad with chickpeas, green beans and potatoes, and a bowl of banana ice cream (made from putting frozen bananas in a food processor)

Dinner: Mac 'n' cheese (the sauce of which is made with tofu, cashews, potatoes and carrots)