Yes, but you accidentally enlarge her

You pull out of Brittany. She looks up at you and snarls "Why'd you stop, loser?" She glances at your cock, throbbing and dripping with precum. "Oh, you are ready to shoot your magic sauce, aren't you, Quickshot?", she grins.

"Fine, let's get this over with, then", Brittany says and strokes her chubby belly. "Remember, ten pounds", she says, looking past you.

You get up on your knees and straddle Brittany's waist. You grab your cock and slowly start to stroke it, taking in Brittany's entire naked body. To you, she is physically perfect as is, even with the few extra pounds on her stomach that she's so **** to get rid of. You try to picture her hourglass figure if your transformation should work.

You stroke with a quicker pace now, trying to fixate on the target area which is Brittany's belly. Your eyes keep drifting up on her body, though. Her massive tits are the biggest you've ever seen in flesh. They're natural, and already bigger than Fatima's blown up tits. You keep thinking they would be the perfect size and shape for a titty fuck you've only experienced in porn.

You stroke and feel like it's time to let go. You look at Brittany's belly and stroke as the waves of orgasm hit you. It's the strongest cumshot you've ever experienced, both physically and mentally. You zone out a little as a massive spurt of semen shoots out from the tip of your cock. "...ten pounds...", Brittany's word echo through your mind as your cumshot flies clean over her belly and splatters all over her chest. You try to recollect your mind and save the situation by aiming back down at her belly. The last spurts, much weaker than the first one, land on Brittany's belly and you chant "lose fat, lose fat" internally.

The splattering of cum wakes up Brittany from her daze. "What the hell, fucker!" is all she manages as both of you study the mess on her chest. Your cum is already working its magic. Ripples of fat travel up from Brittany's stomach and travel up until they stop at her breasts. After a while, her stomach comes to rest, now in the most perfectly flat state you could imagine. Meanwhile, her breasts still continue to grow, gathering fat from out of nowhere. They stop when they're twice as big as Brittany's head, clearly having gained roughly ten pounds.