"Come on out, Sweetie Belle," said Rarity, her tone patient but firm. "Let's inspect the damage."
"This is awfully skimpy, Rarity," Sweetie Belle called, reluctance in her voice.
"All the better to see those problem areas," Rarity replied.
Sweetie Belle reluctantly emerged from the dressing room, wearing her new pink bikini. The scanty swimsuit, which was more string than anything, left little to the imagination. Rarity, dressed in an equally skimpy blue bikini, assessed her little sister.
"Well, you were right to ask me for help, Darling. You’ve always been on the plump side, but now you're looking downright chubby."
Sweetie Belle blushed as she looked down at her mostly bare body. Adolescence had been kind to her chest; her breasts had developed early, and were now a good cup size larger than Rarity's. However, it seemed every inch of growth there was followed by two inches on her waist. What started as a bit of tummy pudge had bloated into a marshmallow-like muffin top. Mom told her not to worry, that she would eventually lose her "filly fat" as she grew taller. Now she had grown taller, and her belly had only grown fatter. Sweetie had begun to worry that her filly fat would never go away on its own, and at last she had gone to Rarity for advice.
Rarity could sense her little sister's unease as she knelt down to inspect her stomach.
"Let's see you suck it in," Rarity instructed.
Sweetie Belle concentrated. She took a deep breath, exhaled completely, lifted her chest, and sucked in her stomach. Her belly receded by an inch or two, but it retained its soft doughy appearance, and it took considerable effort just to maintain the façade for a few seconds.
"Okay. Let it out," Rarity commanded.
Sweetie inhaled rapidly, and with a soft gloop, her stomach bulged out, wobbling a bit before settling back into place.
Rarity sighed wistfully as she poked Sweetie's belly. "I really should have intervened sooner… I didn't realize you had accrued this much filly fat."
"It's all because of the stupid hormones," Sweetie said, pouting.
Now, Rarity's expression became more serious. "You can't blame it all on hormones, Sweetie Belle. I know for a fact that you've been overdoing it on the cookies lately."
Sweetie felt guilt wash over her. It was true. Her walk home from school took her past Sugarcube Corner, and she had been stopping there almost every day for half a dozen chocolate chippers. She reached down to grope her belly, her fingers sinking into the soft fat. Sure enough, it felt a lot like a blob of cookie dough.
"I guess you're right… I never imagined they would all go straight to my belly."
Rarity smiled kindly as she slipped her measuring tape around Sweetie Belle's hips. "I'm afraid you're hopelessly apple-shaped, Darling. I'm more of an hourglass, but even I struggled with my weight when I was your age."
"You were chubby?" Sweetie Belle asked.
Rarity grinned, blushing ever-so-slightly, "Not quite as chubby as you, but I did start high school with a few extra pounds."
"How did you get rid of them?" Sweetie asked, turning her attention to her big sister's perfectly taut stomach. Rarity followed Sweetie's gaze downward.
Rarity chuckled as she realized that, when viewed side-by-side, their tummies looked like the before-and-after shots from a weight-loss ad.
"Well Darling, I realized that if I wanted to lose my filly fat, I had to stop eating like a filly." Rarity said, tipping her nose upward. "I gave up sweets, I took up aerobics, and that was that."
"You make it sound so easy," Sweetie sighed.
Put her arm around her little sister. "Don't fret, Sweetie Belle. Your big sister will show you how to lose weight like a proper young mare! We'll start you on a low-carb diet, with daily cardio exercise and a tummy-toning routine."
Sweetie gulped, "A tummy toning routine?"
"A young lady should always be working on her trouble spots!" Rarity said, once again poking Sweetie's tummy bulge. "And we'll have weekly weigh-ins so you can watch those extra pounds melt away! Doesn't that sound like fun?"
No. Thought Sweetie Belle. It sounds like a lot of work.