It was pretty embarassing for Batgirl as she rode back to the batcave on her motorcycle. The chopper looked so tiny now, that it almost looked like her fat ass was trying to absorb it. The seat was rendered completely invisible already.
Not to mention that her 300 pound plus body slowed down the speed. Clearly even Wayne tech equipment wasn't built for this much weight.
Luckily, aside from a few blank stares from pedestrians, she evntually made it to the cave.

Batman and Robin turned as they heard the engine roaring down the narrow ridge. Robin sighed in relief once Barbarra finally came to a safe stop.
"Sorry I'm late. *RIP!*" Just as Barbarra swung her leg of the bike though, a loud tear was heard. Batman and the boy wonder just stiffed up and saw Barbarra blush. They couldn't see where her costume tore, but Barbarra felt a sudden breeze. She covered her open backdoor with her hands, and walked over to her partners, making sure not to turn her back to them.
Once she made it over, Batman cleared his throat and asked "What took you so long?".
"Oh, I thought I saw one of Harley's henchman left behind, turned out I was wrong, and then the drive here wasn't exactly easy." she explained, becoming slightly ashamed at the end.
"I'll bet." Robin remarked. Barbarra snapped out of her self loathing and socked him "Ow!".

"If you two are finished bickering, I'll bring you up to speed on what were dealing with." Batman turned to the computer and started typing. His sidekicks watched the monitor.
"Chemical V, developed by the US government for warfare, it was originally going to be used as a new form of gas. Any enemy soldiers who breathed it in would be rendered weak with hunger, in theory. First however, the department of defense wanted to see the result of the direct chemical.
The computer displayed an experiment video log.

"I am Professor Anderson, and this is Janine. She has volunteered to test the effects of Chemical V." the man in the lab coat said to the camera. He handed the vile to a woman with red hair, and was wearing a green top and a skirt. She took one sip and stopped "Yuck!".
"How do you feel Janine?" Anderson asked. Suddenly, she fell onto her side, and moaned while clutching her stomach. "It seems that it wor-AH!-*GULP*" before the Proefessor could finish, Janine finished him, by making a meal out of him.
She belched, and patted her fat tummy, before her belt snapped. Then, the tape abruptly stopped as some men came in and restrained her.

"What...what happened to him?" Barbarra managed to mutter. "The agency in charge refused to comment, though judging by this video, I'd say he was, digested." Batman spoke in his commonly ominous tone. Robin shuddered. Barbarra became nervous.
"After this experiment, the President ordered that all amounts of Chemical V be destroyed, the vats in Ajax were apparently awaiting disposal." Batman finished.
"Of all the cities, they had to send some to Gotham, and now Harley's eating people, we need to go after her!" Robin pointed out.
"That can wait!" Barbarra blurted out of from her nervous state. Though she quickly controlled herself thanks to the oncoming stares.
"Calm down Barbarra, I remember the promise I made you, and I already alerted the police Robin, Ajax Chemicals is now under 24 hour servailance." Batman turned back to the computer.
"Thank god my dad is away on work, It'd be hard to explain how his little gymnast now looks like she's ready for Sumo Wrestling." Barbarra said. "I bet Bruce could pay for tickets to Japan." Just as she was about to strike the Boy Wonder again, Batman cleared his throat again. That made them stop.

"So have you found anything that could lead to an antidote?" Batgirl asked. "At this point, no, Chemical V is such an unstable compound, the possibilities for a counter chemical agent are almost too many to count." Barbarra sighed at that answer.
"Right now it will be best if I catalouge what I already know about the component, so far, the effects." a list appeared on the computer screen. Batman continued "Chemical V does do what it was meant to, it creates great hunger in whoever takes it, and I also believe that it may increase the rate of production the body's fat cells absorb nutrients. It clearly also alters the digestive tract, allowing the consumption and digestion of much larger meals, which in doing so leads to more needed fat cells.".

After the explaination, a loud growl echoed through the cave. The dynamic duo turned to see that it was Batgirl's belly " *GURGLE* *BLORP* *CHURN* ".
"Barbarra, are you okay?" Robin asked. Batgirl meanwhile was becoming very nervous again. It was clear that her gut was working on her last meal. Now she was sure they would find out she ate a person. She was worried, so worried, that she didn't notice something else.

*BLAAAAAAAAAAAAAAUUUUUUUUUUURRRRRRRRRRP*

All the stress of possibly being suspected made Barbarra unable to be aware of the gaseous pressure from within her bowels being released.
After choking and gagging on the stench, Batman and Robin were once again forced to place on their gas masks.
"And apparently, it accelerates the production of methane gas." Batman added. "Sorry." Barbarra blushed intensly.
"Just watch where you aim that thing." Robin fanned the air of the somehow visible fart.
"Oh come on, it's not that bad." After Barbarra spoke, a bat fell dead to the ground.

Suddenly, footsteps were heard. Barbarra quickly turned around, causing her body to jiggle. Robin stepped out of the line of fire.
"Begging your pardon master Bruce, but you might want to turn on Channel 4." Alfred informed. After doing so, Batman witnessed one of Gotham's many problems.
"A riot." he groaned. What ever the cause, a huge group of thugs was tearing up the streets.
"Let me go, I need to burn some of this off." Batgirl said.
"Uh, Barb" She looked where Robin pointed, only to see the Batcycle groan, and then break in half. The next thing everyone heard, was a roaring engine as the Dark Knight took off in the Batmobile.

"I'll see if Master Bruce has any reinforced steal lying around." Alfred left. Batgirl sulked.