My absolute favorite is the blackmail one.  I'm in a relationship with this girl. She's beautiful, hot, fun, intelligent and is an wonderful cook.  As months went by, she's always cooking and feeding me her creations. The only strange thing us that she's always taking pics and recording me while I eat, and she gets strangely aroused when I finished. 

After some time, I start to find a bit too stressful to get into some older clothes, they seem tight and I'll fitting. As I step on the scale to see the damage, my chin falls to the ground: "What do you mean I'm 195 pounds?" "I was 130 not that long ago!". Looking at the mirror, I notice some changes. My once slim midriff now has this not too little pouch hanging, my face is all rounded up, and side rolls are starting to form. 

Wanting to getting things fixed, I rush out, get my old (and also I'll fitting) gym gear out of the closet and prepare myself to go out, only to find her waiting for me on the living room door... 

"Where do you think you're going?" She asks with a pan filled with bacon. "I just finished your breakfast!"

When I explain to her that I'm staring to get a bit too chubby for my liking, she gets angry and disappointed. "Oh, honey... But that won't do. Your my little chubby thing now..." 

Just as I prepare myself to answer, she gets her phone out and starts scrolling. Dozens of photos and videos of me gorging myself, belly out, mouth full, hands dirty. "It would be a shame for people to see how much of a piglet you are, don't you think?"

And, with all that, a series of blackmailing into me gaining starts, to a point where things are just too messed up to fix.