Interesting question, and one I have data for! So in the end it depends on your target audience. If you are going for a general audience (like in your question) it is possible, but a bit of a minefield.
So a few games had fat or Weight Gain content in it and some had it on full display and did well. 3 I could think of right of the bat would be:
- Fat Princess - Fat and Feeding
- Overlord 1 & 2 - Fat, Slob, & Gluttony
- Evil Genius - Forced Weight Gain
The way these games got away with it is bc they made it make sense. Fat Princess had a feeding and weight gain mechanic as their central focus but pass it off as subversive, and make it fit with the amazing game play so well you cant imagine it without it. Overlord tends to work it into its themes and for comedic effect. The absurdity of it (since you are supposed to be mocking the forces of good) just fits with the game so well its not questioned. Finally Evil Genius has you fatten up one of the super agents to get rid of them. This is justified by the fact the agent is vain and you find out their worst nightmare is getting fat.
As you can see from the above it really depends on how you implement it. If it feels out of place, forced in, then people will accuse it of being fetish content, but if you can make it it feel like it has a good reason for being there that is not fetish related it will be accepted. But this can be a really hard line to walk.
On the other side you can loose the fetish audience you may be wanting to put it in for if they feel it was toned down to appeal to a general audience (this is bad bc it means the content is out of place enough to feel like it is just there for fetish reasons which means you loose some of your general audience as well). As you can see from this chart from my survey the general trend is towards will not buy:
So to answer your question, I think it is possible, but is very risky as you can turn off both audiences. Its better if you are looking to make a commercial game to choose one audience and go for them.