That was Maia, aka Kardashian. She was just fat. Even on a normal diet for her size and age she packed on the grams because unlike other boas that will cruise the enclosure and hunt when they get hungry, she is the epitome of ambush predator and simply waits in her hide for prey to be dropped in front of her nose. Seriously, I never see her out and about unless she's going potty, and then she's right back under her hide when she's done.
So, she was put on a diet and I make sure to take her out for 15-20 minutes a day every day the week prior to her feeding day to simulate "hunting" before she eats.
The OP's burm is not fat by any stretch. I would just feed it and leave it alone as much as possible for the next few weeks.
OK,
Now I remember, and I'm glad things worked out there with your boa. She was/is a pretty little thing.
Yes,, this snake is very thin however I'm not sure what's going on in the back end.