Prompt: Sherlock has to go undercover over a long period of time to infiltrate a mafia ring... to do so he has to eat at their restaurant every night. he doesn't tell john about this case at first and keeps disappearing. when sherlock starts putting on weight john can't believe it. john starts coming along and eventually they expose the ring, but it takes 6 months (or more) and sherlock has a pretty hefty gut when it's over. john finds he likes it of course!

"Oh for God's sake! JOHN!"

John jumped, startled out of his doze in front of the telly by the angry shout from Sherlock's room.

"Are you alright?" he called, figuring his flatmate had likely set fire to something again. Maybe it was better to let him do his experiments in the kitchen again. At least the parts that required a Bunsen burner.

John hurried to his flatmate's bedroom and pushed the partly open door wider. "What's wrong? Are you hurt?"

The consulting detective spun around on his heel, dark brows furrowed in annoyance and streaked with grey. His hair too was straight and slicked back with grey streaks. An almost comical mustache was clinging to his upper lip. John blinked. If it weren't for that pout he'd wonder who this stranger in his flat was.

"Er-"

"John, I require one of your jumpers. This damn waistcoat won't-" Sherlock snarled, pulling at the garment in question which brought John's eyes down to it as well. He felt his breath catch. It wouldn't button, and surely it would have normally. The shirt beneath waistcoat was struggling as well. The buttons were pulled tight against their holes. That wasn't anything particularly new as far as it pertained to Sherlock, though. What was new was the pale soft skin pressing out between them. John swallowed, then realized Sherlock had said something.

"You... you need what?"

"Your jumper. A roomy one. The one you're wearing should work suitably. It has a certain older man look to it,"said Sherlock, flinging off the waistcoat and starting to undo the buttons. A very soft, very pudgy stomach peeked out over the detective's waistband.

John had been about to protest about Sherlock's assessment of his jumper, but now he once again found himself thoroughly distracted. Sherlock Holmes with a belly was one of the things he thought he'd never see.

"John. Your jumper. Please. I promise I'll return it I just need it for tonight."

"Oh, right." John stripped it off. He passed it over and Sherlock tugged it over himself, pulling it down to cover his new soft little belly.

"You've put on three pounds," Sherlock noted, glancing at John's middle.

John crossed his arms protectively, and sniped, "You're one to talk. Anyway. It's winter. It happens."

Sherlock frowned. "What do you mean?"

"What about your weight gain,eh? That's more than three new pounds there," said John, nodding at Sherlock's now hidden belly.

"Oh. Yes. I... it'll drop off after this case. All that damn pasta," Sherlock grumbled, his cheeks pinking slightly as he rubbed at it.

"So you do have a case on," said John, "That's where you've been disappearing to every night?"

"Yes. It seems to be taking me longer than I expected."

"Why didn't you tell me? I want to help, you know that."

Sherlock gave him the ghost of a smile. "I know you do. But it's been tricky enough coming up with a new disguise every night for myself. One person you can turn into anyone, but two? People begin to notice patterns." Sherlock sighed and for a split second, John saw a round little outline push out from under the jumper.

"So what? You've been eating out at a different restaurant every-"

"No, the same restaurant. One owned by a very influential Italian family," corrected Sherlock, "I'm looking into it on my brother's behalf. I'm starting to wonder if he was just trying to save his diet. Or sabotage mine with endless pastas."

"So you're investigating a pasta Mafia of some kind?" asked John, grinning.

Sherlock grimaced. "I'll thank you not to write this up under that title."

"Wouldn't dream of it," said John, chuckling, then he sobered and suggested, "Maybe I should come with you. You've hit a dead end right? What harm could it do?"

Sherlock pondered it. "None that I can see... we'll need to gray your hair as well however. Here, take these false spectacles as well. That ought to be sufficient."

"And one of my other jumpers?"

"Oh, yes of course. Sorry."

Fifteen minutes later, Sherlock and John had become two gray-haired older men. John leaning on his old cane and Sherlock managing to take a few inches off his height with a very convincing hunch to his back.

They caught a cab and arrived at a small rather quaint looking little restaurant not too far off. The hostess greeted them, smiling and got them seated at a small booth. Sherlock ordered a red wine and an appetizer in a wheezy voice and she bustled off.

"Need an appetizer even with all this bread and olive oil?" murmured John, chuckling and helping himself to a slice. That was certainly a change in the detective's usual capacity.

"Need? No, not really. Though we do need to stay until closing. So eat slowly."

"Blimey," said John, chuckling, "No wonder you've put on a few."

Sherlock rolled his eyes and took a piece of bread as well, munching on it moodily. Their appetizer came and Sherlock warbled a thank you, picking up one of the oysters and scraping it neatly from its shell before eating it with a hum. John eyed them skeptically but took one as well. His eyes widened in surprise.

"Oh, wow. Didn't know I liked those," said John, taking another once he'd swallowed.

"The food is excellent," Sherlock said, smiling slightly, "The restaurant might be a front for a mafia ring, but they certainly know how to cook."

"Thank God," said John, going back for more.

Sherlock grinned. "You may change your tune as the night goes on," he warned, then cheerfully ordered in his disguised voice as the waitress returned.

The pasta really was phenomenal. John had to remind himself to go through it slowly, drag it out rather than just stuffing his face with it all at once. Sherlock was well practiced, clearly, eating slowly but steadily, clearing every bite from his plate methodically, though with clear enjoyment. He looked relaxed and calm behind that odd mustache, even if his eyes were still flicking around the room periodically.

"So what exactly is it you're looking for?" John asked.

"A customer that isn't here for the pasta," answered Sherlock, sitting back once his plate was clean, his belly rounded softly beneath the borrowed jumper he wore, "A customer that might not leave by the main entrance but suddenly... disappear."

John settled back from his own emptied plate and looked around, his hands perched on top of his middle. There were a few couples, a group, a few solitary diners... no one that John could pick out as being there for anything besides a good Italian meal. But then he knew that Sherlock would observe some small detail that would give the crook away. Next was a small antipasto dish of brushetta, fresh tomatoes, and excellent cheeses. Sherlock muffled a burp and adjusted his trousers then asked, "Dessert?"

They each had a large portion of tiramisu. John felt ready to explode, but he knew that if they stopped eating, the bill would likely be next and they still had an hour before the restaurant closed. Several patrons had left already, some new had come in, but none had seemed suspicious in the slightest. Sherlock was looking very much disappointed even as he ate the magnificently tasty dessert. At last he pushed his plate away and leaned back with a huff. A very visible round belly was now visible underneath the previously roomy jumper. Sherlock burped and rubbed it idly, looking around the room. He fetched a smile onto his lips as their waitress returned.

"Two coffees please, then we'll be off. You've been absolutely darling my dear," Sherlock said, looking every inch the sweet older gentleman. John managed a small smile as well, his stomach gurgling.

"Christ, do you always eat this much?" he asked, his tone hushed, his hands clutching his stomach and wanting very much to undo his trousers, "Forget chasing after the crook now. I doubt I could even get out of the booth."

"Hmm... an eventuality that has occurred to me before," said Sherlock, muffling another burp, "But, you get used to it. And for God's sake, John, if you need to unbutton please do. I've had mine undone since the main course."

John swallowed hard, then did as directed, letting out a soft contented sigh as his belly had room to expand. He was dying to take a peek under the table and see just how full Sherlock was looking. Their coffees came and the two men sipped them slowly, the warmth seeping into their overfull bellies, soothing them and relaxing the muscles with the warmth. John almost felt that he was swelling further but it no longer hurt. It just felt... good.

Sherlock, too, looked peaceful as he waved lazily for the bill, paid it, and then set about slowly drawing his coat around himself. John copied him, sucking in his breath in order to do up his trousers again. They both toddled out, bellies full, minds sleepy and waited for a cab as the door was locked behind him.

"Well, there you have it," said Sherlock, "My activities for the past two weeks."

"Hm, not bad. Shame we didn't catch anyone tonight though. You are sure there's a secret mafia behind it?"

"Quite sure. Unless my brother suddenly developed a sense of humor along with a penchant for pranks." Sherlock let out a bark of derisive laughter.

Over the next few weeks, John was starting think that perhaps that development wasn't so far fetched at all. John accompanied Sherlock whenever he could, the two of them changing tactics and deciding that perhaps the best way to catch the criminals was to make their presence known plainly. The investigation still seemed to be requiring an exorbitant amount of pasta. Both doctor and detective returned home every night with a round belly, collapsing onto the sofa and popping their trousers open with a soft groan as their middles expanded outwards. At least the dishes were good enough not to become boring, and there was variety certainly, but God, what John would do for a night without pasta on the menu.

Six months passed much the same way, several pairs of trousers had to be replaced by larger ones. John had grown a steadfast little paunch that refused to shift no matter what forms of exercise he took up. Sherlock, though, Sherlock was approaching plump and portly. He had a proper potbelly now, a gut that hung over his waistband, pushing out against his shirts, pressing against his buttons, rounding up proudly as the detective lay thinking on the sofa. The influx of carbohydrates had tempered the man however, made him more easy going and more prone to sleeping through the night. John thought that an improvement indeed. Well, he found all of it an improvement really. That belly looked so at home on Sherlock's frame that John almost forgot he'd once been a twiggy skeleton of a man. John longed to cuddle up into the new bulge of plump fat, loved the thought of running his fingers over it, rubbing it after Sherlock finished his evening binge and lulling the detective to sleep with soft careful motions. John wondered what it looked like during the meal, gently swelling and rounding up against his waistband until deft fingers released it and it could push down the zipper with its weight and girth. He wondered sometimes if the grunts and soft groans Sherlock made after overeating were similar to those he'd make in more... intimate settings, or if John rubbed and squeezed at the big soft belly Sherlock had collected. The thoughts were very distracting, so much so that John found himself lost in thought when Sherlock finally bellowed "There!" and launched his new bulk at a young man slipping into the kitchen.

Once the criminal had been apprehended and the rest of his family found and exposed by Mycroft's goons, John and Sherlock ambled home. They had decided to walk, the night being unseasonably warm, and the thought being that they both could rather use the exercise. An elegant black car glided up to the curb and a window rolled down. Sherlock's face immediately turned stoney.

"My, my, Brother mine, you are looking well," came a soft smug voice.

"Piss off, Mycroft," the detective snapped in return.

"I merely wanted to thank you, personally. See how you had fare-"

Sherlock blushed, and turned away. "You came to gloat. Childish."

"Only childish when it's you on the receiving end?"

"John, come on."

Sherlock seized his doctor's forearm and pulled him away down another street.

"If you ever need tips on dieting, I have a few I can pass along!" Mycroft called after his little brother. Then the car pulled away. Sherlock was still fuming. He let go of John and stuffed his hands moodily into his coat pockets.

They walked in silence for a time, then John ventured to ask quietly, "Are you planning on losing it?"

Sherlock snorted, "Of course I am! Why would I want to be fat? Fat Sherlock Holmes? I'd be the laughing stock of London! I'd-"

"Okay, okay, just asking," said John. He sighed and followed alongside. "You know, I think you look fine. I don't know why you're so fussed over a few pounds."

"It is not a few pounds, John," Sherlock snarled, "I'm podgy, round, fat! I've got a huge jiggling belly poking out over my trousers!"

"Yeah, okay you do, so what?"

"So-"

"You're still brilliant! You still solved the case, caught one of the mafia members. Actually I doubt you could have held him down like that without your belly," John said allowing himself a chuckle, "Look, what I mean to say is, you're fine. You look great. Better than great actually..."

"You... you mean to say you don't mind me being a bit... more?" said Sherlock, still staring straight ahead.

"Yeah."

"You... you like it. On me?"

"Yes."

Sherlock spun around to look at John. His eyes grew wide as John smirked up at him, took a step closer, his hands drifting down Sherlock's sides, slipping under his coat to squeeze at the new soft flesh there.

"Oh." was all Sherlock managed to say before John pulled him in for a long slow snog.

John smiled up at his detective as the two broke for breath. Sherlock's cheeks looked a bit pink.

"So, Chinese?" asked the ex-army doctor, "I think I've met and exceeded my pasta intake for the next decade."

Sherlock swallowed then nodded, still looking rather dazed. "I... yes. I am a bit hungry. We didn't get past the appetizer."

"Yeah, that's what I was thinking," murmured John, "Can't have my boyfriend going hungry on me. People might think I don't look after you."

Sherlock swallowed, then grinned, "Hm, right you are, my doctor."

He took John's hand and lead the way to their favorite Chinese restaurant for all the fried rice and dumplings Sherlock could possibly eat.