Will snakes go on "hunger strike" even if underweight?

[Bogertophis]

You have to ask yourself "why" is your snake not feeding as well as you expect.

Did you vet check his stool sample for parasites. Could there be anything wrong with his set-up? (high & low temps? humidity? substrate? hides? excessive handling?)

Too much motion from f/t prey DOES turn off a snake...especially shy snakes like BPs. It's important to help build your snake's confidence, believe it or not. BPs are
ambush-predators...feed him at night (normal hunting time) & offer food when he appears to be looking for it (peeking out of his hide). DO NOT approach the snake
with prey dancing from your tongs: instead, make it appear (slight wiggle motions) that the prey is cluelessly wandering past (not approaching but just out of reach)
where the snake is hiding...you want to elicit a slight chase from the snake, & let go when he catches up with it. Then be still...I mean it, really still, or some snakes
detect your motion & drop what they're doing.

BPs rely on heat sensing pits to find the high body temperature of rodents (& similar prey), so if your f/t rodents aren't warm enough, that may be the problem. Thaw
then warm up briefly in very warm water, & many here have the best luck by blasting with blow-dryer right before offering. Have you tried that? Rodents cool off fast,
so you have to be organized at the right time. Sorry, but you did choose a BP, & they are known to be fussy eaters...this just goes with the territory.

How long have you had this snake? Are you feeding him the same rodents (mice or rats, or?) as he was previously raised on? They don't smell or taste the same, and
again, many BPs are picky about this too.

I've never found it helpful to use chicken or tuna broth, btw. It won't likely help or if it seems to, it's just coincidence. Likely other causes...

No telling if this lack of desire to eat has to do with seasonal (cooler temps. & shorter daylight periods) but yes, even snakes that are underweight may refuse to eat now-
this is instinctive. In the wild, snakes that eat too late in the season & get stuck with a stomach full of food in weather too cold to digest can die from this...so those
making this mistake in the past did not survive to pass on their genes...thus, "natural selection" arrived created BPs (& most other snakes) that "know" to stop eating
when the fall/winter temperatures start to drop. In keeping snakes, especially BPs that need warmer temps. & tend to be fussy eaters, you want to keep up the ambient
temps. in the cage and the room where they are...also, consider adding more light in the room to help "fool them". It's hard to correct this situation once your snake has
already gotten chilled & decided it's time to fast.

Before you decide he is "fasting", make sure all other husbandry issues are spot on. Not likely that chicken or tuna broth will make a bit of difference...