After the party, Dash had to admit to herself that there was just no way she could fly back to her cloud house. She felt like she’s about to collapse any minute, and has a very hard time keeping her eyes open.

Twilight, of course, notices. “Rainbow? I think it would be better if you spend the night at the Friendship Castle.”

Uselessly rubbing her tired eye, Dash gives her a tired but grateful smile. “That would be awesome.” But then she remembers that she doesn’t live alone, and turns to her fellow Pegasus friend. “Hey, Fluttershy? Would you mind taking care of Tank for me?”

“Oh, not at all!” The animal loving Pegasus assures.

“Thanks.”

“I hope you’ll feel better tomorrow.” Fluttershy adds, making Dash’s eyes widen. “Oh, I’m sorry, I just thought.. never mind.”

Rainbow wants to ask her what she means, but yawns and almost falls over when she covers her mouth with a hoof.

Twilight engulfs her in her magical aura, regarding the other ponies. “I think it’s time we go. Thanks everyone.”

And then they teleport into Twilight’s castle.

Twilight brought her exhausted friend into one of the many guest rooms in the castle, tucking her into bed. She levitates a glass of water onto the nightstand, as well as a fresh apple. “There. Call if you need anything else, I’m right next door.”

“Thanks, Twi. Really.” Rainbow replies, her voice betraying how exhausted she is.

It doesn’t take long for her to fall asleep.

She dreams of the party they’d had earlier, and eating all the cake and other goods all by herself, completely uncontrollably, until she basically grows into a giant ball with legs and wings, breaking the roof and walls until the building collapses.

Dash wakes up with a startled gasp and sweat dripping down her face. The next thing she knows is that she’s leaning over the side of the bed, dry heaving.

Not a moment later, Twilight teleports herself into Dash’s room with a bright purple flash. She magics the overhead lights on, then tries to comfort her friend until the heaving stops.

“What’s going on?” She asks, deeply worried.

“Bad dream…” Dash grumbles hoarsely, picking up the glass of water and trying to calm down her upset stomach.

“Wanna talk about it?” Twilight offers, wrapping an arm around her friend.

Dash sighs. “We were at that party from earlier, and I ate all the cake and other stuff, all by myself, until I was just a huge… fat… monster.”

Twilight frowns in confusion. “But you barely ate anything at the party.” She points out, trying to make sense of such a dream. “Are you hungry?” She suggests, levitating the apple closer to her.

Dash turns her head away. “No.”

“Hmm…” Twilight puts it back on the nightstand. Then she realises that she could feel Dash’s spine protruding in-between her folded wings as she hugs her. “Rainbow? Have you lost more weight?”

Dash blinks. “No, why?”

“I think you have.” Twilight whispers in horror, backing away a bit to get a real look at her friend. As Dash shifts on the bed to watch Twilight, the alicorn could see every single rib whenever Dash inhales, and her shoulder blades were poking out right in front of her wings. “Rainbow…” she whispers in shock.

The Pegasus frowns, looks down at herself, then back at Twilight, not understanding what has her so upset.

“What? What is it?” She demands.

“Have you looked into a mirror lately?” Twilight asks. Then she remembers that evening of Dash’s first day of training. How she had seemed unhappy with what she’d seen, and then asked Twilight if she thought she looked ‘fat’. As if that word ever belonged in a sentence with her name.

“Uhm, yeah? All the time.” Dash replies. She’d practically gotten stuck in front of them in the shower and locker room at Wonderbolt Headquarters.

“…really?” Twilight asks in doubt. She teleports a full body mirror into the room, holding it up on Dash’s level, who is still sitting on the bed.

But instead of hearing a surprised gasp and other exclamations of distress as Twilight expected, she watches Dash frown the longer she looks at her own reflection.

“I look the same as always, what’s your point?” She demands. It’s the middle of the night, still, and she is still very tired and just wants to get back to sleep. Even if that means having another such nightmare.

Twilight’s mouth falls open. “You don’t- Huh?! How can you not see how thin you are?! I can see all your ribs, even from here!”

Rainbow throws her a dumbfounded look, thinking that this must be some sort of sick joke, because she didn’t see any of that when she looks in the mirror.

She looks back at her reflection, and is disappointed when she looks bloated like a pregnant mare. She turns away in disgust.

“Do you see?” Twilight asks, assuming she’s made a breakthrough.

“All I see is how fat and out of shape I am. Thanks for showing me, but I’d like to go back to sleep now.” Dash deadpans, curling up on the bed and throwing the blanket over herself.

Twilight is utterly speechless. She places the mirror down, thinks about trying to talk to Dash more, but then decides to hit the books in her library. Maybe she could find some answers there.

Four hours later the sun is rising up in the sky, and all that she’d learned is that Pegasus ponies have a much faster metabolism than earth ponies and unicorns, and even alicorns. So pegasi, especially if they’re athletes like Dash is, need a lot of calories and especially proteins to keep themselves healthy. Under-eating results in rapid weight-loss, which Twilight has seen for herself.

This rapid metabolism also explains Dash’s strange energy levels. “Well now I understand why she’s constantly napping and falling asleep in seconds.” She mumbles to herself.

The thing that she couldn’t make sense of is why Dash keeps under-eating. She’d already fit into her Wonderbolt suit, so why is she still not eating?

“TWILIGHT!” Spike shouts from down the hall, running towards her. “Twilight!”

“What is it??” She asks, jumping up.

“Rainbow Dash!” He pants quickly, hands on his knees. “She’s passed out, I can’t wake her up!”

Author's Note

After having multiple people point out Luna’s lack of intervention, I feel like I need to say this, or rather point this out:

In the nightmare episodes (sleepless in ponyville, bloom and gloom) Luna doesn’t act for a looong time, to make the episode happen. Even in the Tantabus episode, she wasn’t aware of all the mane six having nightmares until Twilight sent her letter (for plot convenience I suppose), and at the beginning of ‘May the best pet win’ she doesn’t help Rainbow when she has the nightmare because of the pets, and startles awake after falling endlessly in the dream. I only write what is more or less canon in the show.

In this fic, my Luna is at least aware of Rainbow having these nightmares and taking note of them being rather strange and repetitive, and consults her sister about them in the next chapter.