Okay, so there are two things wrong with the other schools of thought, as listed previously in the chapter choices. And if you asked Reagan, they were pretty damning as far as both her plan, and her general taste for staying alive and un-assaulted by angry athletes.
See, if she told Uma the truth, Uma would probably have actually factually killed her. And if she didn't, she would have at least made Reagan drop two grand on new workout equipment to replace the ones that she had helped to "mysteriously" break down. Uma may have been out of practice, but Reagan knew that she couldn't outrun her even now. Reagan would effectively be signing her own death warrant with (as Lionel Hutz might have called it) The Truth (head-shake)
But the problem with The Truth (head-nod) was that Uma wasn't stupid. This wasn't Phoebe that Reagan was pranking, who was dingier than a jingle bell, and it wasn't Audrey or Chel, who probably would have been too relieved to question Reagan's reassurance and might have chubbed up a bit more out of complacency.
So that ran the riskier course of action—outright telling Uma that she'd put on some weight.
"I meannnnnn..." Reagan winced, "You don't look bad..."
"I knew it!" Uma fell back into her booth dramatically, taking her arms off of the table and pushing away her plate of half-finished tacos, "I knew that it was noticeable. Audrey tried to tell me that I looked fine."
"You do look fine though!" Reagan (in a mild moment of panic) answered quickly, "You're still in better shape than... well, pretty much anyone else that I know personally."
"I guess so, but..."
Her hands found their way back to the table, her fingers wrapped around the handle on the Lone Star beer mug. She took a big frothy gulp and wiped away the head mustache. Her other hand lifted and fell to her stomach. Softer and squishier than ever, and full of a lunch's worth of beer and tacos on top of that, there was some definite roundness to it now. During the brief glimpses of belly that Reagan had snuck, it was getting harder and harder to see any definition on Uma's abdominals.
"Ugh, I feel gross." Uma scrunched her nose, "Like one of those washed-up, coulda-been-contenders that make the bleachers squeak beneath them when they buy a ticket to go relive the glory days in the audience."
"Wow, okay, that's a description." Reagan laughed, "But Uma, you're fine. It's a little pudge. Who cares?"
"Me." Uma paused, "Ugh, I need to get back to the gym."
Crap.
"Better yet, I need to get a new set of exercise equipment." Uma continued to think aloud, "Or at least someone who'll go work out with me..."
Crap crap crap.
This was falling apart, right in front of her. Reagan had to find a way to salvage this plot fast, or else Uma would start trying to slim down. It'd be harder, with the appetite stimulants and the cheap vitamins, but how long until she was back to having a flat tummy, washboard abs, and a (mostly) undeserved sense of self-satisfaction?
For Reagan, to whom Socratic tendencies for Gadflyishness came naturally, there seemed to be only one solution...