Nearly every day for the past few weeks, 21-year-old Anika Mejia has eaten a breakfast of homemade pancakes topped with a scoop of low-fat ice cream. It’s part of her "bikini prep" for the ninth annual Stingrey Classic bodybuilding competition in April — and yes, it’s a meal plan that raises eyebrows.

"When people who aren’t familiar with flexible dieting see what I eat, they are in complete disbelief," Mejia said. "But it’s science, it works."

The 5-foot-1-inch Mejia, who weighs 101 pounds, has been eating this way — flexible dieting — for the past two years. Flexible dieting follows a philosophy that goes by the acronym IIFYM, which stands for "if it fits your macros."

The diet, thought to have originated in the bodybuilding community from athletes tired of eating the same foods, is gaining momentum as a revolutionary way of eating. The idea is that you can successfully manipulate your body composition to cut body fat or make muscle gains without following a restrictive and often mundane diet.

The main rule is to keep track of your intake of three macronutrients: protein, carbohydrates and fat.

Contrary to the traditional "eating clean" diet, which relies on specific nutrient-dense foods and cuts out "junk foods," advocates of flexible dieting say no food is off-limits as long as you stay within your body’s target range for each macronutrient.

The amount of "macros" a person needs is based on that person’s total daily energy expenditure — a calculation that uses age, gender, weight, height and exercise level to estimate the amount of calories needed daily.

Instagram and other social media have helped fuel the popularity of flexible dieting, with proponents posting photos of cupcakes and other calorie- and sugar-rich foods traditionally off-limits to those looking to change their body composition.

Mejia followed a flexible diet to prepare for her first bodybuilding competition in 2013. While many competitors were "eating clean," she was still able to indulge in burritos and pancakes in the weeks leading up to the Paradise Cup. Because of her eating habits, many were skeptical she would do well — but Mejia placed fifth out of 47 women in her division.

Amy Tousman, a registered dietitian, said the idea of following a flexible diet plan is something she generally advocates for long-term results.

"Giving up your favorite foods and making all sorts of restrictive food rules never works in the long run," Tousman said, adding "all foods can fit into a healthy eating pattern."

Tousman emphasized the importance of making healthier choices within each of the macronutrient groups. She recommends high-fiber grains, whole fruits and vegetables, healthy fats and lean meats and plant proteins.

Tousman said flexible dieting is an improvement over many of the fad diets people have been trying.

"But if people use it as a ‘free for all’ it will backfire," Tousman said. "People still need to eat sensibly." 

Alex Steppe, a certified personal trainer and registered dietitian, has worked with weight-management clients and athletes who have seen success with this philosophy.

She said it is important to make the distinction between fitting healthy, balanced meals into your macros versus simply filling it with sodas and Pop-Tarts.

"I do not support using flexible dieting to justify eating a bunch of junk food, whether it fits the macros or not," Steppe said. "It’s not just about calories in or out, it’s about the quality of the food you’re bringing in."

Flexible dieting can be a great way for people to begin making healthy dietary changes, Steppe said. She supports this type of eating as long as it’s paired with metabolic testing. Her personal clients are analyzed by a machine that allows Steppe to prescribe them with specific macronutrient recommendations based on their unique metabolisms.

For beginners, flexible diet advocates recommend simply keeping track of the macronutrients in your diet for the first few months and being mindful of fiber and sugar intake before starting to manipulate meals.

Christian Calio, 20, has followed a flexible diet for more than a year.

He described himself as "the normal guy" who enjoys going to the gym. Prior to counting his macros, Calio would restrict certain foods, which led to gorging on junk food and a guilty conscience.

"It was kind of like an eating disorder in a way. I used to binge a lot in really huge quantities," said Calio, who is 5 feet 7 inches tall and weighs 175 pounds.

He said he prefers flexible dieting because it allows him to eat a wide variety of foods and fit in a few treats without the overwhelming desire to binge.

Calio recommends tracking the numbers through a smartphone app calorie counter. MyFitnessPal is a free app with an online database that breaks down the macronutrients in various foods. But he also carries a portable scale with him.

For Mejia, who has about a month left before her contest, pancakes are still on her daily menu.

She’s come a long way since the days when she feared carbs and sweets. Flexible dieting has made her fitter and happier.

"It’s about finding a balance, enjoying the foods you want when it fits and in moderation," Mejia said. "I am way happier now with a freedom of different food choices."