This is a long shot, but...
TL:DR. There was a YouTube vid of this chick with wide hips, massive tits and a gut in a skin-tight yellow sweater (maybe grey sweatpants too?). It's spilt into 3 sections of her gaining weight in the same yellow v-neck sweater. I reckon the sweater had ¾ length arms?
From memory it's just a torso shot, you can maybe see her chin but no face. Don't think there's any audio but I could be wrong.
It would have been 10-15+ years ago, probably 480p.
I stroked it to this vid so many times but I can't for the life of me remember the name of the video or the account. Gonna do my best to recount it incase anyone remembers it from this description and has saved it.
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It was pretty short, but from memory the girl starts off reasonably chunky, "curvy". The yellow sweater fits. It's a little tight because of the style and because she's got an hourglass figure. She shows off a little, I think she does a turn to give a side view. Her stomach's not flat or fat, just gently rounded like someone who isn't doing ab crunches all the time.
By the second section her hips have widened out a bit, her arms are a bit chubbier and her tits, hips and belly are stretching that sweater out. It still covers her more or less but a person who wasn't into fat girls would look at her and think "Jeez tubby, go a couple of sizes up already...". She's outgrown it enough that you're getting a tiny bit of cleavage now.
She shows off her side view so you can see how much her belly's filled out, she's looking nice and plump, but probably still on the upper end of "thick".
Then the third section.
She's huge. She's really porked up a lot between sections 2 and 3. Still technically has an "hourglass" figure I guess, but swear to god her hips seemed like they were twice the width they were in the first part. Her upper arms are looking fat, her neck looks softer, from memory even her forearms and wrists are getting a little chunky. She's got a visible double belly that the sweater can't cover, and fabric is stretched so tight across her gut that you can see the indentation of her navel. She's moving a little slower, the way a girl who's recently gained a ton of weight does, like she's still adjusting to having all this extra fat weighing her down, and she runs her hands across her body like she's really enjoying it.
And her tits are EXPLODING out the top of the V-neck. One of the best parts for teenage me was that her nipples looked like they were rock hard and pushing against the fabric of the sweater, which they aren't in the previous two sections. Whether she's actually turned on or it's just how fat her tits have gotten combined with her being in a too-small pushup or shaper bra for this section or whatever, it looks like she's turned on by her gain, it's hot. She does her little turn and her belly sticks out properly now, I think her tits still beat it but it's close. Pulls her gut and hips out over the waistband, from memory she's got a good bit of belly hang now.
She pulls the sweater down to try and cover her gut (not happening) and bends over towards the camera so you get a better look at how much more cleavage she's got now (a lot). From memory this is generally the point where I bust
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Memory's a bit hazy about this but I think she only had one other video on her account where you couldn't really see much of her, maybe her in a corset or something? But that yellow sweater one.....incredible quick nut material.
Would be wildly lucky if anyone had saved an obscure YouTube video from almost two decades ago, but even if not, that vid's burned into my memory. Definitely helped cement how much I love a fat girl who is also WIDE, you know?